Exj 25

XJ EMISSION CONTROL SYSTEMS 25 - 1

EMISSION CONTROL SYSTEMS
CONTENTS

page page

EVAPORATIVE EMISSION CONTROLS . . . . . . . 11 ON-BOARD DIAGNOSTICS . . . . . . . . . . . . . . . . . 1

ON-BOARD DIAGNOSTICS

INDEX
page page

GENERAL INFORMATION LOAD VALUE . . . . . . . . . . . . . . . . . . . . . . . . . . 10
SYSTEM DESCRIPTION . . . . . . . . . . . . . . . . . . 1 MALFUNCTION INDICATOR LAMP (MIL) . . . . . . 1
DESCRIPTION AND OPERATION MONITORED SYSTEMS . . . . . . . . . . . . . . . . . . 7
CIRCUIT ACTUATION TEST MODE . . . . . . . . . . 2 NON-MONITORED CIRCUITS . . . . . . . . . . . . . . 9
COMPONENT MONITORS . . . . . . . . . . . . . . . . . 9 STATE DISPLAY TEST MODE . . . . . . . . . . . . . . 2
DIAGNOSTIC TROUBLE CODES . . . . . . . . . . . . 2 TRIP DEFINITION . . . . . . . . . . . . . . . . . . . . . . . 9
HIGH AND LOW LIMITS . . . . . . . . . . . . . . . . . . 10

GENERAL INFORMATION PCM). Because the condition happens at an engine
speed above the maximum threshold (2000 rpm), the
SYSTEM DESCRIPTION PCM will not store a DTC.
The Powertrain Control Module (PCM) monitors There are several operating conditions for which
many different circuits in the fuel injection, ignition, the PCM monitors and sets DTC’s. Refer to Moni-
emission and engine systems. If the PCM senses a tored Systems, Components, and Non-Monitored Cir-
problem with a monitored circuit often enough to cuits in this section.
indicate an actual problem, it stores a Diagnostic
Trouble Code (DTC) in the PCM’s memory. If the NOTE: Various diagnostic procedures may actually
code applies to a non-emissions related component or cause a diagnostic monitor to set a DTC. For
system, and the problem is repaired or ceases to instance, pulling a spark plug wire to perform a
exist, the PCM cancels the code after 40 warm-up spark test may set the misfire code. When a repair
cycles. Diagnostic trouble codes that affect vehicle is completed and verified, connect the DRB scan
emissions illuminate the Malfunction Indicator tool to the 16–way data link connector (Fig. 1) to
(check engine) Lamp. Refer to Malfunction Indicator erase all DTC’s and extinguish the MIL.
Lamp in this section.
Technicians can display stored DTC’s by three dif-
Certain criteria must be met before the PCM
ferent methods. Refer to Diagnostic Trouble Codes in
stores a DTC in memory. The criteria may be a spe-
this section. For DTC information, refer to charts in
cific range of engine RPM, engine temperature,
this section.
and/or input voltage to the PCM.
The PCM might not store a DTC for a monitored
circuit even though a malfunction has occurred. This DESCRIPTION AND OPERATION
may happen because one of the DTC criteria for the
circuit has not been met. For example , assume the MALFUNCTION INDICATOR LAMP (MIL)
diagnostic trouble code criteria requires the PCM to As a functional test, the MIL (check engine) illumi-
monitor the circuit only when the engine operates nates at key-on before engine cranking. Whenever
between 750 and 2000 RPM. Suppose the sensor’s the Powertrain Control Module (PCM) sets a Diag-
output circuit shorts to ground when engine operates nostic Trouble Code (DTC) that affects vehicle emis-
above 2400 RPM (resulting in 0 volt input to the sions, it illuminates the MIL. If a problem is

16–WAY DATA LINK CON-
NECTOR

25 - 2 EMISSION CONTROL SYSTEMS XJ
DESCRIPTION AND OPERATION (Continued)
State Display Inputs and Outputs or State Display
Sensors.

CIRCUIT ACTUATION TEST MODE
The Circuit Actuation Test Mode checks for proper
operation of output circuits or devices the Powertrain
Control Module (PCM) may not internally recognize.
The PCM attempts to activate these outputs and
allow an observer to verify proper operation. Most of
the tests provide an audible or visual indication of
device operation (click of relay contacts, fuel spray,
etc.). Except for intermittent conditions, if a device
functions properly during testing, assume the device,
its associated wiring, and driver circuit work cor-
rectly. Connect the DRB scan tool to the data link
connector and access the Actuators screen.

DIAGNOSTIC TROUBLE CODES
A Diagnostic Trouble Code (DTC) indicates the
Fig. 1 Data Link (Diagnostic) Connector Location PCM has recognized an abnormal condition in the
detected, the PCM sends a message to the instru- system.
ment cluster to illuminate the lamp. The PCM illu- The technician can retrieve and display DTC’s in
minates the MIL only for DTC’s that affect vehicle three different ways:
emissions. There are some monitors that may take • The preferred and most accurate method of
two consecutive trips, with a detected fault, before retrieving a DTC is by using the DRB scan tool. The
the MIL is illuminated. The MIL stays on continu- scan tool supplies detailed diagnostic information
ously when the PCM has entered a Limp-In mode or which can be used to more accurately diagnose
identified a failed emission component. Refer to the causes for a DTC.
Diagnostic Trouble Code charts in this group for • The second method is by observing the two-digit
emission related codes. number displayed at the Malfunction Indicator Lamp
Also, the MIL either flashes or illuminates contin- (MIL). The MIL is displayed on the instrument panel
uously when the PCM detects active engine misfire. as the Check Engine lamp. This method is to be used
Refer to Misfire Monitoring in this section. as a “quick-test” only. Always use the DRB scan tool
Additionally, the PCM may reset (turn off) the MIL for detailed information.
when one of the following occur: • The third method is by observing the two-digit
• PCM does not detect the malfunction for 3 con- number displayed at the vehicle odometer. This
secutive trips (except misfire and Fuel system Moni- method, similar to the MIL lamp, is also to be used
tors). as a “quick-test” only.
• PCM does not detect a malfunction while per- Remember that DTC’s are the results of a sys-
forming three successive engine misfire or fuel system or circuit failure, but do not directly iden-
tem tests. The PCM performs these tests while the tify the failed component or components.
engine is operating within Ϯ 375 RPM of and within
NOTE: For a list of DTC’s, refer to the charts in this
10 % of the load of the operating condition at which
section.
the malfunction was first detected.

STATE DISPLAY TEST MODE BULB CHECK
The switch inputs to the Powertrain Control Mod- Each time the ignition key is turned to the ON
ule (PCM) have two recognized states; HIGH and position, the malfunction indicator (check engine)
LOW. For this reason, the PCM cannot recognize the lamp on the instrument panel should illuminate for
difference between a selected switch position versus approximately 2 seconds then go out. This is done for
an open circuit, a short circuit, or a defective switch. a bulb check.
If the State Display screen shows the change from
HIGH to LOW or LOW to HIGH, assume the entire OBTAINING DTC’S USING DRB SCAN TOOL
switch circuit to the PCM functions properly. Connect (1) Connect the DRB scan tool to the data link
the DRB scan tool to the data link connector and (diagnostic) connector. This connector is located in
access the state display screen. Then access either

the passenger compartment; at the lower edge of An example of a flashed DTC is as follows:
instrument panel; near the steering column. • Lamp flashes 4 times, pauses, and then flashes
(2) Turn the ignition switch on and access the 6 more times. This indicates a DTC code number 46.
“Read Fault” screen. • Lamp flashes 5 times, pauses, and flashes 5
(3) Record all the DTC’s and “freeze frame” infor- more times. This indicates a DTC code number 55. A
mation shown on the DRB scan tool. DTC 55 will always be the last code to be displayed.
(4) To erase DTC’s, use the “Erase Trouble Code” This indicates the end of all stored codes.
data screen on the DRB scan tool. Do not erase any
DTC’s until problems have been investigated OBTAINING DTC’S USING VEHICLE
and repairs have been performed. ODOMETER
(1) Cycle the ignition key On - Off - On - Off - On
OBTAINING DTC’S USING MIL LAMP within 5 seconds.
(1) Cycle the ignition key On - Off - On - Off - On (2) After a short pause, the mileage shown on the
within 5 seconds. vehicles digital odometer will be temporarily deleted.
(2) Count the number of times the MIL (check After this occurs, read the DTC number displayed on
engine lamp) on the instrument panel flashes on and the odometer. Each two–digit number will be dis-
off. The number of flashes represents the trouble played with a slight delay between numbers.
code. There is a slight pause between the flashes rep- (3) A DTC number 55 will always be the last code
resenting the first and second digits of the code. to be displayed. This indicates the end of all stored
Longer pauses separate individual two digit trouble codes. After code 55 has been displayed, the odometer
codes. will return to its normal mode.

DIAGNOSTIC TROUBLE CODE DESCRIPTIONS

GENERIC
MIL SCAN DRB SCAN TOOL DESCRIPTION OF DIAGNOSTIC TROUBLE
HEX CODE
CODE TOOL DISPLAY CODE
CODE
12* Battery Disconnect Direct battery input to PCM was disconnected
within the last 50 Key-on cycles.
55* Completion of fault code display on Check
Engine lamp.
01 54** P0340 No Cam Signal at No camshaft signal detected during engine
PCM cranking.
02 53** P0601 Internal Controller PCM Internal fault condition detected.
Failure
05 47*** Charging System Battery voltage sense input below target
Voltage Too Low charging during engine operation. Also, no
significant change detected in battery voltage
during active test of generator output circuit.
06 46*** Charging System Battery voltage sense input above target
Voltage Too High charging voltage during engine operation.
0A 42* Auto Shutdown Relay An open or shorted condition detected in the
Control Circuit auto shutdown relay circuit.
0B 41*** Generator Field Not An open or shorted condition detected in the
Switching Properly generator field control circuit.
0C 37** P0743 Torque Converter An open or shorted condition detected in the
Clutch Soleniod/Trans torque converter part throttle unlock solenoid
Relay Circuits control circuit (3 speed auto RH trans. only).
0E 35** P1491 Rad Fan Control An open or shorted condition detected in the
Relay Circuit low speed radiator fan relay control circuit.


GENERIC
HEX CODE
CODE
0F 34* Speed Control An open or shorted condition detected in the
Solenoid Circuits Speed Control vacuum or vent solenoid circuits.
10 33* A/C Clutch Relay An open or shorted condition detected in the
Circuit A/C clutch relay circuit.
12 31** P0443 EVAP Purge Solenoid An open or shorted condition detected in the
Circuit duty cycle purge solenoid circuit.
13 27** P0203 Injector #3 Control Injector #3 output driver does not respond
Circuit properly to the control signal.
or
14 P0202 Injector #2 Control Injector #2 output driver does not respond
or
19 25** P0505 Idle Air Control Motor A shorted or open condition detected in one or
Circuits more of the idle air control motor circuits.
1A 24** P0122 Throttle Position Throttle position sensor input below the
Sensor Voltage Low minimum acceptable voltage
or
1B P0123 Throttle Position Throttle position sensor input above the
Sensor Voltage High maximum acceptable voltage.
1E 22** P0117 ECT Sensor Voltage Engine coolant temperature sensor input below
Too Low minimum acceptable voltage.
or
1F P0118 ECT Sensor Voltage Engine coolant temperature sensor input above
Too High maximum acceptable voltage.
21 17* Engine Is Cold Too Engine did not reach operating temperature
Long within acceptable limits.
23 15** P0500 No Vehicle Speed No vehicle speed sensor signal detected during
Sensor Signal road load conditions.
24 14** P0107 MAP Sensor Voltage MAP sensor input below minimum acceptable
Too Low voltage.
or
25 P0108 MAP Sensor Voltage MAP sensor input above maximum acceptable
Too High voltage.
27 13** P1297 No Change in MAP No difference recognized between the engine
From Start to Run MAP reading and the barometric (atmospheric)
pressure reading from start-up.
28 11* No Crank Reference No crank reference signal detected during
Signal at PCM engine cranking.
2B P0351 Ignition Coil #1 Peak primary circuit current not achieved with
Primary Circuit maximum dwell time.
2C 42* No ASD Relay Output An Open condition Detected In The ASD Relay
Voltage at PCM Output Circuit.


GENERIC
HEX CODE
CODE
31 63** P1696 PCM Failure Unsuccessful attempt to write to an EEPROM
EEPROM Write location by the PCM.
Denied
39 23** P0112 Intake Air Temp Intake air temperature sensor input below the
Sensor Voltage Low maximum acceptable voltage.
or
3A P0113 Intake Air Temp Intake air temperature sensor input above the
Sensor Voltage High minimum acceptable voltage.
3D 27** P0204 Injector #4 Control Injector #4 output driver does not respond
3E 21** P0132 Upstream O2S Oxygen sensor input voltage maintained above
Shorted to Voltage the normal operating range.
44 53** PO600 PCM Failure SPI PCM internal fault condition detected
Communications
45 27** P0205 Injector #5 Control Injector #5 output driver does not respond
or
52 77* SPD CTRL PWR RLY; Malfuntion detected with power feed to speed
or S/C 12V Driver control servo solenoids
CKT
56 34* Speed Control Switch Speed control switch input above the maximum
Always High acceptable voltage.
or
57 Speed Control Switch Speed control switch input below the minimum
Always Low acceptable voltage.
65 42* Fuel Pump Relay An open or shorted condition detected in the
Control Circuit fuel pump relay control circuit.
66 21** P0133 Upstream O2S Slow Oxygen sensor response slower than minimum
Response required switching frequency.
or
67 P0135 Upstream O2S Heater Upstream oxygen sensor heating element
Failure circuit malfunction
69 P0141 Downstream or Oxygen sensor heating element circuit
Pre-Catalyst Heater malfunction.
Failure
6A 43** P0300 Multiple Cylinder Misfire detected in multiple cylinders.
Mis-fire
or
6B P0301 Cylinder #1 Mis-fire Misfire detected in cylinder #1.
or
6C P0302 Cylinder #2 Mis-fire Misfire detected in cylinder #2.
or


GENERIC
HEX CODE
CODE
6D P0303 Cylinder #3 Mis-fire Misfire detected in cylinder #3.
or
6E P0304 Cylinder #4 Mis-fire Misfire detected in cylinder #4.
70 72** P0420 Efficency Failure Catalyst efficiency below required level.
71 31* P0441 Evap Purge Flow Insufficient or excessive vapor flow detected
Monitor Failure during evaporative emission system operation.
72 37** P1899 P/N Switch Stuck in Incorrect input state detected for the Park/
Park or in Gear Neutral switch, auto. trans. only.
76 52** P0172 Fuel System Rich A rich air/fuel mixture has been indicated by an
abnormally lean correction factor.
77 51** P0171 Fuel System Lean A lean air/fuel mixture has been indicated by an
abnormally rich correction factor.
7E 21** P0138 Downstream and Oxygen sensor input voltage maintained above
Pre-Catalyst O2S the normal operating range.
Shorted to Voltage
80 17** P0125 Closed Loop Temp Engine does not reach 20°F within 5 minutes
Not Reached with a vehicle speed signal.
84 24** P0121 TPS Voltage Does TPS signal does not correlate to MAP sensor
Not Agree With MAP
87 14** P1296 No 5 Volts To MAP 5 Volt output to MAP sensor open.
Sensor
8A 25** P1294 Target Idle Not Actual idle speed does not equal target idle
Reached speed.
94 37* P0740 Torq Conv Clu, No Relationship between engine speed and vehicle
RPM Drop At Lockup speed indicates no torque converter clutch
engagement (auto. trans. only).
95 42* Fuel Level Sending Open circuit between PCM and fuel gauge
Unit Volts Too Low sending unit.
or
96 Fuel Level Sending Circuit shorted to voltage between PCM and
Unit Volts Too High fuel gauge sending unit.
or
97 Fuel Level Unit No No movement of fuel level sender detected.
Change Over Miles
99 44** P1493 Ambient/Batt Temp Battery temperature sensor input voltage below
Sen VoltsToo Low an acceptable range.
or
9A P1492 Ambient/Batt Temp Battery temperature sensor input voltage above
Sensor VoltsToo High an acceptable range.
9B 21** P0131 Upstream O2S O2 sensor voltage too low, tested after cold
Shorted to Ground start.
or


GENERIC
HEX CODE
CODE
9C P0137 Downstream and O2 sensor voltage too low, tested after cold
Pre-Catalyst O2S start.
Shorted to Ground
9D 11** P1391 Intermittent Loss of Intermittent loss of either camshaft or
CMP or CKP crankshaft position sensor
AE 43** P0305 Cylinder #5 Mis-fire Misfire detected in cylinder #5.
or
AF P0306 Cylinder #6 Mis-fire Misfire detected in cylinder #6.
BA 11** P1398 Mis-fire Adaptive CKP sensor target windows have too much
Numerator at Limit variation
CO 21 P0133 CAT MON SLOW O2 A slow switching oxygen sensor has been
1/1 detected in bank 1/1 during catalyst monitor
test.
* Check Engine Lamp (MIL) will not illuminate if this Diagnostic Trouble Code was recorded. Cycle Ignition
key as described in manual and observe code flashed by Check Engine lamp.
** Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was
recorded.
*** Generator Lamp illuminated

MONITORED SYSTEMS MIL 21—OXYGEN SENSOR (O2S) MONITOR
There are new electronic circuit monitors that Effective control of exhaust emissions is achieved
check fuel, emission, engine and ignition perfor- by an oxygen feedback system. The most important
mance. These monitors use information from various element of the feedback system is the O2S. The O2S
sensor circuits to indicate the overall operation of the is located in the exhaust path. Once it reaches oper-
fuel, engine, ignition and emission systems and thus ating temperature 300° to 350°C (572° to 662°F), the
the emissions performance of the vehicle. sensor generates a voltage that is inversely propor-
The fuel, engine, ignition and emission systems tional to the amount of oxygen in the exhaust. The
monitors do not indicate a specific component prob- information obtained by the sensor is used to calcu-
lem. They do indicate that there is an implied prob- late the fuel injector pulse width. This maintains a
lem within one of the systems and that a specific 14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio,
problem must be diagnosed. the catalyst works best to remove hydrocarbons (HC),
If any of these monitors detect a problem affecting carbon monoxide (CO) and nitrogen oxide (NOx) from
vehicle emissions, the Malfunction Indicator (Check the exhaust.
Engine) Lamp will be illuminated. These monitors The O2S is also the main sensing element for the
generate Diagnostic Trouble Codes that can be dis- Catalyst and Fuel Monitors.
played with the check engine lamp or a scan tool. The O2S can fail in any or all of the following
The following is a list of the system monitors: manners:
• Misfire Monitor • slow response rate
• Fuel System Monitor • reduced output voltage
• Oxygen Sensor Monitor • dynamic shift
• Oxygen Sensor Heater Monitor • shorted or open circuits
• Catalyst Monitor Response rate is the time required for the sensor to
All these system monitors require two consecutive switch from lean to rich once it is exposed to a richer
trips with the malfunction present to set a fault. than optimum A/F mixture or vice versa. As the sen-
Following is a description of each system monitor, sor starts malfunctioning, it could take longer to
and its DTC. detect the changes in the oxygen content of the
Refer to the appropriate Powertrain Diagnos- exhaust gas.
tics Procedures manual for diagnostic proce- The output voltage of the O2S ranges from 0 to 1
dures. volt. A good sensor can easily generate any output

voltage in this range as it is exposed to different con- The PCM is programmed to maintain the optimum
centrations of oxygen. To detect a shift in the A/F air/fuel ratio of 14.7 to 1. This is done by making
mixture (lean or rich), the output voltage has to short term corrections in the fuel injector pulse width
change beyond a threshold value. A malfunctioning based on the O2S sensor output. The programmed
sensor could have difficulty changing beyond the memory acts as a self calibration tool that the engine
threshold value. controller uses to compensate for variations in engine
specifications, sensor tolerances and engine fatigue
MIL 21—OXYGEN SENSOR HEATER MONITOR over the life span of the engine. By monitoring the
If there is an oxygen sensor (O2S) shorted to volt- actual fuel-air ratio with the O2S sensor (short term)
age DTC, as well as a O2S heater DTC, the O2S and multiplying that with the program long-term
fault MUST be repaired first. Before checking the (adaptive) memory and comparing that to the limit,
O2S fault, verify that the heater circuit is operating it can be determined whether it will pass an emis-
correctly. sions test. If a malfunction occurs such that the PCM
Effective control of exhaust emissions is achieved cannot maintain the optimum A/F ratio, then the
by an oxygen feedback system. The most important MIL will be illuminated.
element of the feedback system is the O2S. The O2S
is located in the exhaust path. Once it reaches oper- MIL 64—CATALYST MONITOR
ating temperature 300° to 350°C (572 ° to 662°F), the To comply with clean air regulations, vehicles are
sensor generates a voltage that is inversely propor- equipped with catalytic converters. These converters
tional to the amount of oxygen in the exhaust. The reduce the emission of hydrocarbons, oxides of nitro-
information obtained by the sensor is used to calcu- gen and carbon monoxide.
late the fuel injector pulse width. This maintains a Normal vehicle miles or engine misfire can cause a
14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio, catalyst to decay. A meltdown of the ceramic core can
the catalyst works best to remove hydrocarbons (HC), cause a reduction of the exhaust passage. This can
carbon monoxide (CO) and nitrogen oxide (NOx) from increase vehicle emissions and deteriorate engine
the exhaust. performance, driveability and fuel economy.
The voltage readings taken from the O2S sensor The catalyst monitor uses dual oxygen sensors
are very temperature sensitive. The readings are not (O2S’s) to monitor the efficiency of the converter. The
accurate below 300°C. Heating of the O2S sensor is dual O2S’s sensor strategy is based on the fact that
done to allow the engine controller to shift to closed as a catalyst deteriorates, its oxygen storage capacity
loop control as soon as possible. The heating element and its efficiency are both reduced. By monitoring
used to heat the O2S sensor must be tested to ensure the oxygen storage capacity of a catalyst, its effi-
that it is heating the sensor properly. ciency can be indirectly calculated. The upstream
The O2S sensor circuit is monitored for a drop in O2S is used to detect the amount of oxygen in the
voltage. The sensor output is used to test the heater exhaust gas before the gas enters the catalytic con-
by isolating the effect of the heater element on the verter. The PCM calculates the A/F mixture from the
O2S sensor output voltage from the other effects. output of the O2S. A low voltage indicates high oxy-
gen content (lean mixture). A high voltage indicates a
MIL 43—MISFIRE MONITOR low content of oxygen (rich mixture).
Excessive engine misfire results in increased cata- When the upstream O2S detects a lean condition,
lyst temperature and causes an increase in HC emis- there is an abundance of oxygen in the exhaust gas.
sions. Severe misfires could cause catalyst damage. A functioning converter would store this oxygen so it
To prevent catalytic convertor damage, the PCM can use it for the oxidation of HC and CO. As the
monitors engine misfire. converter absorbs the oxygen, there will be a lack of
The Powertrain Control Module (PCM) monitors oxygen downstream of the converter. The output of
for misfire during most engine operating conditions the downstream O2S will indicate limited activity in
(positive torque) by looking at changes in the crank- this condition.
shaft speed. If a misfire occurs the speed of the As the converter loses the ability to store oxygen,
crankshaft will vary more than normal. the condition can be detected from the behavior of
the downstream O2S. When the efficiency drops, no
MIL 51/52—FUEL SYSTEM MONITOR chemical reaction takes place. This means the con-
To comply with clean air regulations, vehicles are centration of oxygen will be the same downstream as
equipped with catalytic converters. These converters upstream. The output voltage of the downstream
reduce the emission of hydrocarbons, oxides of nitro- O2S copies the voltage of the upstream sensor. The
gen and carbon monoxide. The catalyst works best only difference is a time lag (seen by the PCM)
when the Air Fuel (A/F) ratio is at or near the opti- between the switching of the O2S’s.
mum of 14.7 to 1.

To monitor the system, the number of lean-to-rich COMPONENT MONITORS
switches of upstream and downstream O2S’s is There are several components that will affect vehi-
counted. The ratio of downstream switches to cle emissions if they malfunction. If one of these com-
upstream switches is used to determine whether the ponents malfunctions the Malfunction Indicator
catalyst is operating properly. An effective catalyst Lamp (Check Engine) will illuminate.
will have fewer downstream switches than it has Some of the component monitors are checking for
upstream switches i.e., a ratio closer to zero. For a proper operation of the part. Electrically operated
totally ineffective catalyst, this ratio will be one-to- components now have input (rationality) and output
one, indicating that no oxidation occurs in the device. (functionality) checks. Previously, a component like
The system must be monitored so that when cata- the Throttle Position sensor (TPS) was checked by
lyst efficiency deteriorates and exhaust emissions the PCM for an open or shorted circuit. If one of
increase to over the legal limit, the MIL (check these conditions occurred, a DTC was set. Now there
engine lamp) will be illuminated. is a check to ensure that the component is working.
This is done by watching for a TPS indication of a
TRIP DEFINITION greater or lesser throttle opening than MAP and
The term “Trip” has different meanings depending engine rpm indicate. In the case of the TPS, if engine
on what the circumstances are. If the MIL (Malfunc- vacuum is high and engine rpm is 1600 or greater
tion Indicator Lamp) is OFF, a Trip is defined as and the TPS indicates a large throttle opening, a
when the Oxygen Sensor Monitor and the Catalyst DTC will be set. The same applies to low vacuum if
Monitor have been completed in the same drive cycle. the TPS indicates a small throttle opening.
When any Emission DTC is set, the MIL on the All open/short circuit checks or any component that
dash is turned ON. When the MIL is ON, it takes 3 has an associated limp in will set a fault after 1 trip
good trips to turn the MIL OFF. In this case, it with the malfunction present. Components without
depends on what type of DTC is set to know what a an associated limp in will take two trips to illumi-
“Trip” is. nate the MIL.
For the Fuel Monitor or Mis-Fire Monitor (contin- Refer to the Diagnostic Trouble Codes Description
uous monitor), the vehicle must be operated in the Charts in this section and the appropriate Power-
“Similar Condition Window” for a specified amount of train Diagnostic Procedure Manual for diagnostic
time to be considered a Good Trip. procedures.
If a Non-Contiuous OBDII Monitor, such as:
• Oxygen Sensor NON-MONITORED CIRCUITS
• Catalyst Monitor The PCM does not monitor the following circuits,
• Purge Flow Monitor systems and conditions that could have malfunctions
• Leak Detection Pump Monitor (if equipped) causing driveability problems. The PCM might not
• EGR Monitor (if equipped) store diagnostic trouble codes for these conditions.
• Oxygen Sensor Heater Monitor However, problems with these systems may cause the
fails twice in a row and turns ON the MIL, re-run- PCM to store diagnostic trouble codes for other sys-
ning that monitor which previously failed, on the tems or components. For example, a fuel pressure
next start-up and passing the monitor is considered problem will not register a fault directly, but could
to be a Good Trip. cause a rich/lean condition or misfire. This could
If any other Emission DTC is set (not an OBDII cause the PCM to store an oxygen sensor or misfire
Monitor), a Good Trip is considered to be when the diagnostic trouble code
Oxygen Sensor Monitor and Catalyst Monitor have
been completed; or 2 Minutes of engine run time if FUEL PRESSURE
the Oxygen Sensor Monitor or Catalyst Monitor have The fuel pressure regulator controls fuel system
been stopped from running. pressure. The PCM cannot detect a clogged fuel
It can take up to 2 Failures in a row to turn on the pump inlet filter, clogged in-line fuel filter, or a
MIL. After the MIL is ON, it takes 3 Good Trips to pinched fuel supply or return line. However, these
turn the MIL OFF. After the MIL is OFF, the PCM could result in a rich or lean condition causing the
will self-erase the DTC after 40 Warm-up cycles. A PCM to store an oxygen sensor or fuel system diag-
Warm-up cycle is counted when the ECT (Engine nostic trouble code.
Coolant Temperature Sensor) has crossed 160°F and
has risen by at least 40°F since the engine has been SECONDARY IGNITION CIRCUIT
started. The PCM cannot detect an inoperative ignition coil,
fouled or worn spark plugs, ignition cross firing, or
open spark plug cables.

CYLINDER COMPRESSION system devices. However, these could cause the PCM
The PCM cannot detect uneven, low, or high engine to store a MAP sensor diagnostic trouble code and
cylinder compression. cause a high idle condition.

EXHAUST SYSTEM PCM SYSTEM GROUND
The PCM cannot detect a plugged, restricted or The PCM cannot determine a poor system ground.
leaking exhaust system, although it may set a fuel However, one or more diagnostic trouble codes may
system fault. be generated as a result of this condition. The mod-
ule should be mounted to the body at all times, also
FUEL INJECTOR MECHANICAL during diagnostic.
MALFUNCTIONS
The PCM cannot determine if a fuel injector is PCM CONNECTOR ENGAGEMENT
clogged, the needle is sticking or if the wrong injector The PCM may not be able to determine spread or
is installed. However, these could result in a rich or damaged connector pins. However, it might store
lean condition causing the PCM to store a diagnostic diagnostic trouble codes as a result of spread connec-
trouble code for either misfire, an oxygen sensor, or tor pins.
the fuel system.
HIGH AND LOW LIMITS
EXCESSIVE OIL CONSUMPTION The PCM compares input signal voltages from each
Although the PCM monitors engine exhaust oxygen input device with established high and low limits for
content when the system is in closed loop, it cannot the device. If the input voltage is not within limits
determine excessive oil consumption. and other criteria are met, the PCM stores a diagnos-
tic trouble code in memory. Other diagnostic trouble
THROTTLE BODY AIR FLOW code criteria might include engine RPM limits or
The PCM cannot detect a clogged or restricted air input voltages from other sensors or switches that
cleaner inlet or filter element. must be present before verifying a diagnostic trouble
code condition.
VACUUM ASSIST
The PCM cannot detect leaks or restrictions in the
vacuum circuits of vacuum assisted engine control

LOAD VALUE
ENGINE IDLE/NEUTRAL 2500 RPM/NEUTRAL
All Engines 2% to 8% of Maximum Load 9% to 17% of Maximum Load

FUEL FWD
SUPPLY
TUBE EVAP CANISTER VENT LINE FILTER/FUEL PRES-
ALIGNMENT ARROW FUEL SURE REGULATOR
ROLLOVERALVE
FUEL V PUMP
RETAINERCLAMP
MODULE
LOCKNUT
PIGTAIL HARNESS


EVAPORATIVE EMISSION CONTROLS

INDEX
page page

DESCRIPTION AND OPERATION DIAGNOSIS AND TESTING
CRANKCASE VENTILATION SYSTEM . . . . . . . 12 VACUUM SCHEMATICS . . . . . . . . . . . . . . . . . . 13
DUTY CYCLE EVAP CANISTER PURGE REMOVAL AND INSTALLATION
SOLENOID . . . . . . . . . . . . . . . . . . . . . . . . . . 11 DUTY CYCLE EVAP CANISTER PURGE
EVAP CANISTER . . . . . . . . . . . . . . . . . . . . . . . 11 SOLENOID . . . . . . . . . . . . . . . . . . . . . . . . . . 14
EVAPORATION (EVAP) CONTROL SYSTEM . . 11 EVAP CANISTER . . . . . . . . . . . . . . . . . . . . . . . 13
ROLLOVER VALVE . . . . . . . . . . . . . . . . . . . . . . 11 ROLLOVER VALVE(S) . . . . . . . . . . . . . . . . . . . 14
VEHICLE EMISSION CONTROL INFORMATION SPECIFICATIONS
(VECI) LABEL . . . . . . . . . . . . . . . . . . . . . . . . 13 TORQUE CHART . . . . . . . . . . . . . . . . . . . . . . . 14

DESCRIPTION AND OPERATION
EVAPORATION (EVAP) CONTROL SYSTEM
The function of the EVAP control system is to pre-
vent the emissions of gasoline vapors from the fuel
tank into the atmosphere. When fuel evaporates in
the fuel tank, the vapors pass through vent hoses or
tubes to a carbon filled EVAP canister. They are tem-
porarily held in the canister until they can be drawn
into the intake manifold when the engine is running.
All engines use a duty cycle purge system. The
PCM controls vapor flow by operating the duty cycle
EVAP purge solenoid. Refer to Duty Cycle EVAP
Canister Purge Solenoid for additional information.
The EVAP canister is a feature on all models for
the storage of fuel vapors from the fuel tank.

NOTE: The hoses used in this system are specially
manufactured. If replacement becomes necessary, it
is important to use only fuel resistant hose. Fig. 1 Rollover Valve Location
On RHD models, the canister is located in the left
ROLLOVER VALVE side of the engine compartment near the heater
blower motor (Fig. 3). The EVAP canister is filled
The fuel tank is equipped with a rollover valve.
with granules of an activated carbon mixture. Fuel
The valve is located on the top of the fuel tank (Fig.
vapors entering the EVAP canister are absorbed by
1). The valve will prevent fuel flow through the fuel
the charcoal granules.
tank vent (EVAP) hoses in the event of an accidental
Fuel tank pressure vents into the EVAP canister.
vehicle rollover. The EVAP canister draws fuel vapors
Fuel vapors are temporarily held in the canister until
from the fuel tank through this valve.
they can be drawn into the intake manifold. The duty
The valve cannot be serviced separately. If replace-
cycle EVAP canister purge solenoid allows the EVAP
ment is necessary, the fuel tank must be replaced.
canister to be purged at predetermined times and at
Refer to Fuel Tank Removal/Installation in Group 14,
certain engine operating conditions.
Fuel System.

EVAP CANISTER DUTY CYCLE EVAP CANISTER PURGE SOLENOID
The Duty Cycle EVAP Canister Purge Solenoid reg-
A maintenance free, EVAP canister is used on all
ulates the rate of vapor flow from the EVAP canister
vehicles. On conventional left hand drive (LHD) mod-
to the intake manifold. The Powertrain Control Mod-
els, the EVAP canister is located in the engine com-
ule (PCM) operates the solenoid.
partment on the passenger side frame rail (Fig. 2).

MOUNTINGTRAP
S FWD MOUNTINGTRAP
SMOUNTING STRAP CANISTER
EVAPSTRAP BOLT
BOLT FWD
EVAP CANISTER
MOUNTING MOUNTING SOLE- INLETCONNECTOR
PURGE BOLT COVER ELECTRICAL
FIXED ORIFICE
AIR FITTING
NOID
AIR
FILTER TING
FIT- VACUUM
HARNESS

it. The solenoid will not operate properly unless it is
installed correctly.

Fig. 2 EVAP Canister Location—LHD Models

Fig. 4 Duty Cycle EVAP Purge Solenoid (LHD
Shown)
CRANKCASE VENTILATION SYSTEM
All 2.5L 4–cylinder and 4.0L 6–cylinder engines
are equipped with a Crankcase Ventilation (CCV)
system (Fig. 5) or (Fig. 6). The CCV system performs
the same function as a conventional PCV system, but
does not use a vacuum controlled valve.

Fig. 3 EVAP Canister Location—RHD Models
During the cold start warm-up period and the hot
start time delay, the PCM does not energize the sole-
noid. When de-energized, no vapors are purged. The
PCM de-energizes the solenoid during open loop oper-
ation.
The engine enters closed loop operation after it
reaches a specified temperature and the time delay
ends. During closed loop operation, the PCM cycles
(energizes and de-energizes) the solenoid 5 or 10
times per second, depending upon operating condi-
tions. The PCM varies the vapor flow rate by chang-
ing solenoid pulse width. Pulse width is the amount
of time that the solenoid is energized. The PCM
adjusts solenoid pulse width based on engine operat-
ing condition.
Fig. 5 CCV System—2.5L Engine—Typical
On vehicles equipped with Left Hand Drive (LHD),
the solenoid attaches to a bracket located in the On 4.0L 6 cylinder engines, a molded vacuum tube
right-rear side of engine compartment near the EVAP connects manifold vacuum to top of cylinder head
canister (Fig. 4). On vehicles equipped with Right (valve) cover at dash panel end. The vacuum fitting
Hand Drive (RHD), the solenoid attaches to a bracket contains a fixed orifice of a calibrated size. It meters
located in the left-rear side of engine compartment. the amount of crankcase vapors drawn out of the
The top of the solenoid has the word UP or TOP on engine.

AIR INLET TING
FIT- FWDIXED
F ORIFICE
FITTING
AIR COVER
FILTER FWD VECI LABEL
MOUNTINGTRAP
S EVAPSTRAP BOLT
MOUNTING
CANISTER


Fig. 7 VECI Label Location—Typical
DIAGNOSIS AND TESTING
VACUUM SCHEMATICS
A vacuum schematic for emission related items can
be found on the Vehicle Emission Control Informa-
Fig. 6 CCV System—4.0L Engine—Typical tion (VECI) Label. Refer to VECI Label in this group
On 2.5L 4 cylinder engines, a fitting on drivers for label location.
side of cylinder head (valve) cover contains the
metered orifice. It is connected to manifold vacuum.
A fresh air supply hose from the air cleaner is con- REMOVAL AND INSTALLATION
nected to front of cylinder head cover on 4.0L
engines. It is connected to rear of cover on 2.5L EVAP CANISTER
engines. On vehicle equipped with Left Hand Drive (LHD),
When the engine is operating, fresh air enters the the EVAP canister is located in engine compartment
engine and mixes with crankcase vapors. Manifold on right side frame rail (Fig. 8). On vehicles equipped
vacuum draws the vapor/air mixture through the with Right Hand Drive (RHD), the canister is located
fixed orifice and into the intake manifold. The vapors on left side of engine compartment near heater
are then consumed during combustion. blower motor (Fig. 9).

VEHICLE EMISSION CONTROL INFORMATION
(VECI) LABEL
All vehicles are equipped with a combined VECI
label. This label is located in the engine compart-
ment (Fig. 7) and contains the following:
• Engine family and displacement
• Evaporative family
• Emission control system schematic
• Certification application
• Engine timing specifications (if adjustable)
• Idle speeds (if adjustable)
• Spark plug and gap
The label also contains an engine vacuum sche-
matic. There are unique labels for vehicles built for
sale in the state of California and the country of
Canada. Canadian labels are written in both the Fig. 8 EVAP Canister Location—LHD Models
English and French languages. These labels are per- REMOVAL
manently attached and cannot be removed without (1) Disconnect vacuum lines at EVAP canister.
defacing information and destroying label. Note location of lines before removal.

MOUNTINGTRAP
S MOUNTING STRAP FWD
BOLT
EVAP CANISTER

REMOVAL AND INSTALLATION (Continued)

Fig. 9 EVAP Canister Location—RHD Models Fig. 10 Duty Cycle EVAP Canister Purge Solenoid—
(LHD Shown)
(2) Remove canister retaining strap bolt.
(3) Remove canister from vehicle. INSTALLATION
(1) Install EVAP canister purge solenoid and its
INSTALLATION mounting bracket to cowl panel.
(1) Position canister into bracket. (2) Tighten bolt to 5 N·m (45 in. lbs.) torque.
(2) Install and tighten strap bolt to 5 N·m (45 in. (3) Connect vacuum harness and wiring connector.
lbs.) torque.
(3) Connect vacuum lines at EVAP canister. ROLLOVER VALVE(S)
The pressure relief/rollover valves(s) are/is molded
DUTY CYCLE EVAP CANISTER PURGE SOLENOID into the fuel tank and are not serviced separately. If
replacement is necessary, the fuel tank must be
REMOVAL replaced. Refer to Fuel Tank Removal/Installation in
On vehicles equipped with Left Hand Drive (LHD), Group 14, Fuel System for procedures.
the solenoid attaches to a bracket located in the
right-rear side of engine compartment near the EVAP
canister (Fig. 10). On vehicles equipped with Right SPECIFICATIONS
Hand Drive (RHD), the solenoid attaches to a bracket
located in the left-rear side of engine compartment. TORQUE CHART
The top of the solenoid has the word UP or TOP on
it. The solenoid will not operate properly unless it is Description Torque
installed correctly. EVAP Canister Mounting Bolt . . . 5 N·m (45 in. lbs.)
(1) Disconnect electrical wiring connector at sole- EVAP Canister Purge Solenoid
noid. Bracket-to-Body Mounting Bolt . 5 N·m (45 in. lbs.)
(2) Disconnect vacuum harness at solenoid.
(3) Remove solenoid and its support bracket.

XJ EMISSION CONTROL SYSTEM 25 - 1

EMISSION CONTROL SYSTEM
CONTENTS

page page

EXHAUST EMISSION CONTROLS—2.5L DIESEL ON-BOARD DIAGNOSTICS—2.5L DIESEL
ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

ON-BOARD DIAGNOSTICS—2.5L DIESEL ENGINE

INDEX
page page

GENERAL INFORMATION DESCRIPTION AND OPERATION
SYSTEM DESCRIPTION—2.5L DIESEL ENGINE DIAGNOSTIC TROUBLE CODES . . . . . . . . . . . . 2
....................................... 1

GENERAL INFORMATION MONITORED CIRCUITS
The MSA can detect certain problems in the elec-
SYSTEM DESCRIPTION—2.5L DIESEL ENGINE trical system.
The 2.5L diesel MSA controller and Powertrain Open or Shorted Circuit – The MSA can deter-
Control Module (PCM) monitor and control many dif- mine if sensor output (which is the input to MSA is
ferent circuits in the fuel injection pump and engine within proper range. It also determines if the circuit
systems. If the MSA senses a problem with a moni- is open or shorted.
tored circuit that indicates an actual problem, a Output Device Current Flow – The MSA senses
Diagnostic Trouble Code (DTC) will be stored in the whether the output devices are electrically connected.
PCM’s memory, and eventually may illuminate the If there is a problem with the circuit, the MSA
Diesel Glow Plug lamp constantly while the key is senses whether the circuit is open, shorted to ground
on. If the problem is repaired, or is intermittent, the (–), or shorted to (+) voltage.
PCM will erase the DTC after 40 warm-up cycles. A
warm-up cycle consists of starting the vehicle when NON–MONITORED CIRCUITS
the engine is cold, then the engine to warms up to a The MSA does not monitor the following circuits,
certain temperature, and finally, the engine tempera- systems or conditions that could have malfunctions
ture falls to a normal operating temperature, then that result in driveability problems. A DTC will not
the key is turned off. be displayed for these conditions.
Certain criteria must be met for a DTC to be Fuel Pressure: Fuel pressure is controlled by the
entered into PCM memory. The criteria may be a fuel injection pump. The PCM cannot detect prob-
specific range of engine rpm, engine or fuel tempera- lems in this component.
ture and/or input voltage to the PCM. A DTC indi- Cylinder Compression: The MSA cannot detect
cates that the PCM has identified an abnormal uneven, low, or high engine cylinder compression.
signal in a circuit or the system. A DTC may indicate Exhaust System: The MSA cannot detect a
the result of a failure, but never identify the failed plugged, restricted or leaking exhaust system.
component directly. Fuel Injector Malfunctions: The MSA cannot
There are several operating conditions that the determine if the fuel injector is clogged, or the wrong
MSA does not monitor and set a DTC for. Refer to injector is installed. The fuel injectors on the diesel
the following Monitored Circuits and Non–Monitored engine are not controlled by the MSA, although a
Circuits in this section. defective fuel injector sensor is monitored by the
PCM.

25 - 2 EMISSION CONTROL SYSTEM XJ
GENERAL INFORMATION (Continued)
Vacuum Assist: Leaks or restrictions in the vac- DESCRIPTION AND OPERATION
uum circuits of vacuum assisted engine control sys-
tem devices are not monitored by the MSA. DIAGNOSTIC TROUBLE CODES
MSA System Ground: The MSA cannot deter- On the following pages, a list of DTC’s is provided
mine a poor system ground. However, a DTC may be for the 2.5L diesel engine. A DTC indicates that the
generated as a result of this condition. PCM has recognized an abnormal signal in a circuit
MSA/PCM Connector Engagement: The MSA or the system. A DTC may indicate the result of a
cannot determine spread or damaged connector pins. failure, but most likely will not identify the failed
However, a DTC may be generated as a result of this component directly.
condition.
ACCESSING DIAGNOSTIC TROUBLE CODES
HIGH AND LOW LIMITS A stored DTC can be displayed through the use of
The MSA compares input signal voltages from each the DRB III scan tool. The DRB III connects to the
input device. It will establish high and low limits data link connector. The data link connector is
that are programmed into it for that device. If the located under the instrument panel near bottom of
input voltage is not within specifications and other the steering column (Fig. 1).
DTC criteria are met, a DTC will be stored in mem-
ory. Other DTC criteria might include engine rpm
limits or input voltages from other sensors or
switches. The other inputs might have to be sensed
by the MSA when it senses a high or low input volt-
age from the control system device in question.

Fig. 1 Data Link Connector Location—Typical
ERASING TROUBLE CODES
After the problem has been repaired, use the DRB
III scan tool to erase a DTC.

MSA CONTROLLER DRBIII CODES

Generic Scan Tool Code DRB III Scan Tool Display
P0100 Mass of Volumes of Air Flow Plausibility
Mass of Volumes of Air Flow Signal High Exceeded
Mass of Volumes of Air Flow Signal Low Exceeded
P0115 Temperature of Engine Coolant SRC High Exceeded
Temperature of Engine Coolant SRC Low Exceeded
P0180 Fuel Temperature Sensor SRC High Exceeded
Fuel Temperature Sensor SRC Low Exceeded
P0400 EGR Open Circuit
EGR Short Circuit
P0500 Vehicle Speed Sensor PEC Frequency Too High
Vehicle Speed Sensor Signal High Exceeded
Vehcle Speed Sensor Plausibility
P0725 Engine Speed Sensor Dynamic Plausibility
Engine Speed Sensor Over Speed Recognition
Engine Speed Sensor Static Plausibilty
P1105 Atmospheric Pressure Sensor SRC High Exceeded
Atmospheric Pressure Sensor SRC Low Exceeded
P1201 Needle Movement Sensor High Exceeded
Needle Movement Sensor Low Exceeded
P1220 Fuel Quantity Actuator Neg. Gov. Deviation Cold
Fuel Quantity Actuator Neg. Gov. Deviation Warm
Fuel Quantity Actuator Pos. Gov. Deviation Cold
Fuel Quantity Actuator Pos. Gov. Deviation Warm
P1225 Control Sleeve Sensor Signal High Exceeded
Control Sleeve Sensor Start End Pos. Not Attained
Control Sleeve Sensor Stop End Pos. Not Attained
P1230 Timing Control Negative Governing Governor Deviation
Timing Control Positive Governing Governor Deviation
P1515 Accelerator Pedal Postion Sensor Signal High Exceeded
Accelerator Pedal Sensor Signal Low Exceeded
Accelerator Pedal Sensor Signal PWG Plaus With Low Idle Switch
Accelerator Pedal Sensor Signal PWG Plaus With Potentiometer
P1600 Battery Voltage SRC High Exceeded
P1605 Terminal #15 Plausibility After Startup
P1610 Regulator Lower Regulator Limit
Regulator Upper Regulator Limit
P1615 Microcontroller Gate-Array Monitoring
Microcontroller Gate-Array Watchdog
Microcontroller Prepare Fuel Quantity Stop
Microcontroller Recovery Was Occurred
Microcontrller Redundant Overrun Monitoring
P1630 Solenoid Valve Controller Open Circuit
Solenoid Valve Controller Short Circuit


Generic Scan Tool Code DRB III Scan Tool Display
P1635 Glow Relay Controller Open Circuit
Glow Relay Controller Short Circuit
P1650 Diagnostic Lamp Open Circuit
Diagnostic Lamp Short Circuit
P1660 Redundant Emer. Stop Plausibility In After-Run
Redundant Emer Stop Powerstage Defective
P1665 Cruise Status Indicator Lamp Short Circuit
P1680 EEPROM Plausibility Checksum Error for Adj.
EEPROM Plausibility Checksum Error in CC212
EEPROM Plausibility Communication With EEPROM
EEPROM Plausibility Func. Switch Wrong or Missing
EEPROM Plausibility Ver Number Not Corresponding
P1685 Vehicle Theft Alarm Code Line Breakdown
P1703 Brake Signal Plaus With Redundant Contact
P1740 Clutch Signal Plausibilty
P1725 Inductive Aux. Speed Sensor Dynamic Plausibilty
Inductive Aux. Speed Sensor Overspeed Recognition
Inductive Aux Speed Sensor Plausibilty
Inductive Aux. Speed Sensor Static Plausibilty

PCM DRBIII CODES

Generic Scan Tool Code DRBIII Scan Tool Display
P0117 Engine Coolant Volts Lo
P0118 Engine Coolant Volts Hi
P0500 Vehicle Speed Signal
P0601 Internal Self Test
P1296 5 VDC Output
P1391 Loss of Cam or Crank


EXHAUST EMISSION CONTROLS—2.5L DIESEL ENGINE

INDEX
page page

DESCRIPTION AND OPERATION REMOVAL AND INSTALLATION
EXHAUST GAS RECIRCULATION (EGR) EGR TUBE . . . . . . . . . . . . . . . . . . . . . . . . ..... 7
SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . ..... 5 EGR VALVE . . . . . . . . . . . . . . . . . . . . . . . ..... 7
VACUUM HOSE ROUTING SCHEMATIC . ..... 5 ELECTRIC VACUUM MODULATOR (EVM) ..... 7
DIAGNOSIS AND TESTING SPECIFICATIONS
EGR GAS FLOW TEST . . . . . . . . . . . . . . ..... 6 TORQUE CHART—2.5L DIESEL . . . . . . . ..... 8
ELECTRIC VACUUM MODULATOR (EVM)
TEST . . . . . . . . . . . . . . . . . . . . . . . . . . ..... 7

DESCRIPTION AND OPERATION EXHAUST GAS RECIRCULATION (EGR) SYSTEM
VACUUM HOSE ROUTING SCHEMATIC GENERAL INFORMATION
Vacuum for the EGR system is supplied by the The EGR system reduces oxides of nitrogen (NOx)
internal engine mounted vacuum pump. Refer to in the engine exhaust. This is accomplished by allow-
EGR System Operation for vacuum pump informa- ing a predetermined amount of hot exhaust gas to
tion. Vacuum harness routing for emission related recirculate and dilute the incoming fuel/air mixture.
components is displayed in (Fig. 1). A malfunctioning EGR system can cause engine
stumble, sags or hesitation, rough idle, engine stall-
ing and poor driveability.

EGR SYSTEM OPERATION
The system consists of:
• An EGR valve assembly. The valve is located
behind the intake manifold (Fig. 2).

Fig. 1 Typical Hose Routing

Fig. 2 EGR Valve and Tube Location

• An Electric Vacuum Modulator (EVM). The EVM The EGR system will be shut down by the MSA
is sometimes referred to as the EGR control solenoid after 60 seconds of continuous engine idling to
or EGR duty cycle solenoid. The EVM serves two dif- improve idle quality.
ferent functions. One is to control vacuum bleed–off
of the EGR valve. The other is to control the “on
time” of the EGR valve. DIAGNOSIS AND TESTING
• The MSA operates the EVM. The MSA is located
is located inside the vehicle in the center consule. EGR GAS FLOW TEST
• An EGR tube (Fig. 2) connecting a passage in Use the following test procedure to determine if
the EGR valve to the rear of the exhaust manifold. exhaust gas is flowing through the EGR valve. It can
• The vacuum pump supplies vacuum for the also be used to determine if the EGR tube is plugged,
EVM and the EGR valve. This pump also supplies or the system passages in the intake or exhaust man-
vacuum for operation of the power brake booster. The ifolds are plugged.
pump is located internally in the front of the engine This is not to be used as a complete test of the
block (Fig. 3) and is driven by the crankshaft gear. EGR system.
The engine must be started, running and warmed
to operating temperature for this test.
(1) All EGR valves are equipped with a vacuum
supply fitting located on the EGR valve vacuum
motor (Fig. 2).
(2) Disconnect the rubber hose from the vacuum
supply fitting (Fig. 2).
(3) Connect a hand–held vacuum pump to this fit-
ting.
(4) Start the engine.
(5) Slowly apply 10 inches of vacuum to the fitting
on the EGR valve motor. Vacuum should hold steady
at 10 inches. If not, replace the EGR valve. If vac-
uum holds steady at 10 inches, proceed to next step.
(6) While applying vacuum, and with the engine
running at idle speed, the idle speed should drop, a
rough idle may occur, or the engine may even stall.
Fig. 3 Internal Vacuum Pump This is indicating that exhaust gas is flowing through
• Vacuum lines and hoses to connect the various the EGR tube between the intake and exhaust man-
components. ifolds.
When the MSA supplies a variable ground signal (7) If the engine speed did not change, the EGR
to the EVM, EGR system operation starts to occur. valve may be defective, the EGR tube may be
The MSA will monitor and determine when to supply plugged with carbon, or the passages in the intake
and remove this variable ground signal. This will and exhaust manifolds may be plugged with carbon.
depend on inputs from the engine coolant tempera- (a) Remove EGR valve from engine. Refer to
ture, throttle position and engine speed sensors. EGR Valve Removal in this group.
When the variable ground signal is supplied to the (b) Apply vacuum to the vacuum motor fitting
EVM, vacuum from the vacuum pump will be and observe the stem on the EGR valve. If the
allowed to pass through the EVM and on to the EGR stem is moving, it can be assumed that the EGR
valve with a connecting hose. valve is functioning correctly. The problem is in
Exhaust gas recirculation will begin in this order either a plugged EGR tube or plugged passages at
when: the intake or exhaust manifolds. Refer to step (c).
• The MSA determines that EGR system operation If the stem will not move, replace the EGR valve.
is necessary. (c) Remove the EGR tube between the intake
• The engine is running to operate the vacuum and exhaust manifolds. Check and clean the EGR
pump. tube and its related openings on the manifolds.
• A variable ground signal is supplied to the EVM. Refer to EGR Tube in this group for procedures.
• Variable vacuum passes through the EVM to the Do not attempt to clean the EGR valve. If the
EGR valve. valve shows evidence of heavy carbon build–up near
• The inlet seat (poppet valve) at the bottom of the base, replace it.
the EGR valve opens to dilute and recirculate
exhaust gas back into the intake manifold.

DIAGNOSIS AND TESTING (Continued)
ELECTRIC VACUUM MODULATOR (EVM) TEST (3) Loosen fitting at exhaust manifold end of tube
(Fig. 2).
VACUUM TEST (4) Remove EGR tube and discard old gasket.
With the engine running, disconnect the vacuum (5) Clean gasket mating surfaces and EGR tube
supply line at the fitting on the EVM. Minimum vac- flange gasket surfaces.
uum should be no less than 20 inches. If vacuum is (6) Check for signs of leakage or cracked surfaces
lower, check for leaks in vacuum supply line. If leaks at both ends of tube, exhaust manifold and EGR
cannot be found, check for low vacuum at vacuum valve.
pump. Refer to Group 5, Brake System for proce-
dures. INSTALLATION
(1) Install a new gasket to EGR valve end of EGR
tube.
REMOVAL AND INSTALLATION (2) Position EGR tube to engine.
(3) Loosely tighten fitting at exhaust manifold end
EGR VALVE of tube.
(4) Install 2 mounting bolts at EGR valve end of
REMOVAL tube. Tighten bolts to 23 N·m (204 in. lbs.) torque.
(1) Remove the rubber hose from turbocharger to (5) Tighten fitting at exhaust manifold end of tube.
metal tube. (6) Install hose from turbocharger to metal tube.
(2) Disconnect vacuum line at EGR valve vacuum
supply fitting (Fig. 2). ELECTRIC VACUUM MODULATOR (EVM)
(3) Loosen the tube fitting at exhaust manifold end The EVM (EGR Duty Cycle Purge Solenoid) is
of EGR tube (Fig. 2). mounted to the side of the PDC.
(4) Remove the two bolts retaining the EGR tube
to the side of EGR valve (Fig. 2). REMOVAL
(5) Remove the two EGR valve mounting bolts (1) Disconnect both cables from battery, negative
(Fig. 2) and remove EGR valve. cable first.
(6) Discard both of the old EGR mounting gaskets. (2) Remove 2 screws holding PDC to bracket,
swing out of way.
INSTALLATION (3) Remove nut and clamp holding battery to bat-
(1) Clean the intake manifold of any old gasket tery tray (Fig. 4).
material.
(2) Clean the end of EGR tube of any old gasket
material.
(3) Position the EGR valve and new gasket to the
intake manifold.
(4) Install two EGR valve mounting bolts. Do not
tighten bolts at this time.
(5) Position new gasket between EGR valve and
EGR tube.
(6) Install two EGR tube bolts. Tighten all four
mounting bolts to 23 N·m (204 in. lbs.).
(7) Tighten EGR tube fitting at exhaust manifold.
(8) Connect vacuum line to EGR valve.
(9) Install the rubber hose from turbocharger to
metal tube.

EGR TUBE
The EGR tube connects the EGR valve to the rear
of the exhaust manifold (Fig. 2).

REMOVAL
(1) Remove rubber hose from turbocharger to
metal tube.
(2) Remove two EGR tube mounting bolts at EGR Fig. 4 Battery Clamp
valve end of tube (Fig. 2).
(4) Remove battery from vehicle.
(5) Disconnect two vacuum hoses at EVM.

REMOVAL AND INSTALLATION (Continued)
(6) Remove mounting screws of EVM. SPECIFICATIONS
(7) Remove the EVM to gain access to the EVM
electrical connector. TORQUE CHART—2.5L DIESEL
(8) Remove electrical connector at EVM.
Description Torque
INSTALLATION
(1) Install electrical connector to EVM. EGR Valve Mounting Bolts . . . 23 N·m (204 in. lbs.)
(2) Install EVM and tighten mounting screws. EGR Tube Mounting Bolts . . . . 23 N·m (204 in. lbs.)
(3) Connect vacuum hoses. EVM (Electric Vacuum Modulator)
(4) Install PDC to bracket and tighten mounting Mounting Bolt . . . . . . . . . . . . . 2 N·m (20 in. lbs.)
screws.
(5) Install battery.
(6) Connect battery cables positive first.

Exj 25

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (17)

Similar a Exj 25

Similar a Exj 25 (20)

Más de Åge Færestrand

Más de Åge Færestrand (20)

Último

Último (20)

Exj 25