Jeep XJ. Manual — part 631
Symptom:
*CHECKING THE EGR SYSTEM
POSSIBLE CAUSES
ASD RELAY OUTPUT CIRCUIT OPEN
EGR VALVE
GROUND CIRCUIT OPEN
VACUUM SUPPLY HOSE
TEST
ACTION
APPLICABILITY
1
Disconnect the Vacuum Supply Hose at the EGR solenoid.
Connect a vacuum gauge to the Vacuum Supply Hose.
Start the engine and allow the engine to idle.
Is the vacuum above 10 inches of mercury at idle?
All
Yes
→
No
→
Repair leaking or restricted Vacuum Supply Hose or faulty
Vacuum Supply Pump.
Perform ROAD TEST VERIFICATION - VER-2.
2
Turn the ignition off.
Disconnect the EGR Solenoid harness connector.
Turn the ignition on.
Using a 12-volt test light connected to ground, check the ASD Relay Output circuit at
the EGR Solenoid harness connector.
Is the test light on?
All
Yes
→
No
→
Repair the ASD Relay Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
3
Turn the ignition off.
Disconnect the EGR Solenoid harness connector.
Using a 12-volt test light connected to 12-volts, check the Ground circuit in the EGR
Solenoid harness connector.
Is the test light on?
All
Yes
→
No
→
Repair the Ground circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
4
NOTE: The Vacuum Output Hose must not be leaking or restricted for the
result of this test to be valid.
Turn the ignition off.
Disconnect the Vacuum Supply and Vacuum Output Hoses in the EGR Solenoid
vacuum connector.
Connect the Vacuum Supply Hose to the Vacuum Output Hose.
Test drive the vehicle and observe vehicle performance.
Is there a power reduction on vehicle acceleration?
All
Yes
→
Test Complete.
No
→
Replace the EGR Valve.
Perform ROAD TEST VERIFICATION - VER-2.
176
DRIVEABILITY - DIESEL
Symptom:
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION
POSSIBLE CAUSES
ACTUATE THE RADIATOR FAN RELAY WITH THE DRB
CHECK FOR FAN CONTROL DTCS
RADIATOR FAN RELAY - SHORTED
RADIATOR FAN RELAY OUTPUT CIRCUIT SHORTED TO VOLTAGE
FUSED B+ CIRCUIT OPEN
SUBSTITUTE RADIATOR FAN RELAY
RADIATOR FAN RELAY OUTPUT CIRCUIT OPEN
RADIATOR FAN GROUND CIRCUIT OPEN
RADIATOR FAN - OPEN
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRB, check for ECM Fan Control DTCs.
Are any Fan Control DTCs present?
All
Yes
→
Refer to symptom list for problems related to the Fan Control
DTCs.
Perform ROAD TEST VERIFICATION - VER-2.
No
→
2
Turn the ignition on.
With the DRB, actuate the Radiator Fan Relay and observe the Radiator Fan.
Did the Radiator Fan cycle on and off?
All
Yes
→
The test is complete.
Perform ROAD TEST VERIFICATION - VER-2.
Radiator Fan inoperative
Radiator Fan always on
3
Turn the ignition off.
Remove the Radiator Fan Relay from the PDC.
Using a 12-volt test light connected to ground, check the Fused B+ circuit.
Did the test light illuminate brightly?
All
Yes
→
No
→
Repair the Fused B+ circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
177
DRIVEABILITY - DIESEL
TEST
ACTION
APPLICABILITY
4
Turn the ignition off.
Install a substitute relay in place of the Radiator Fan Relay.
Turn the ignition on.
With the DRB, actuate the Radiator Fan Relay.
Does the Radiator Fan cycle on and off?
All
Yes
→
Replace the Radiator Fan Relay.
Perform ROAD TEST VERIFICATION - VER-2.
No
→
5
Turn the ignition off.
Remove the Radiator Fan Relay from the PDC.
Disconnect the Radiator Fan harness connector.
Connect a fused jumper wire between the Fused B+ circuit cavity and the Radiator
Fan Relay Output circuit cavity in the Radiator Fan Relay connector.
Using a 12-volt test light connected to ground, check the Radiator Fan Relay Output
circuit in the Radiator Fan harness connector.
Did the test light illuminate brightly?
All
Yes
→
No
→
Repair the Radiator Fan Relay Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
6
Turn the ignition off.
Disconnect the Radiator Fan harness connector.
Using a 12-volt test light connected to 12-volts, check the Radiator Fan Ground
circuit.
Did the test light illuminate brightly?
All
Yes
→
No
→
Repair the Radiator Fan Ground circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
7
If there are no possible causes remaining, view repair.
All
Repair
Replace the Radiator Fan.
Perform ROAD TEST VERIFICATION - VER-2.
8
Turn the ignition off.
Remove the Radiator Fan Relay from the PDC.
Disconnect the Radiator Fan harness connector.
Turn the ignition on.
Measure the voltage of the Radiator Fan Relay Output circuit.
Is the voltage above 0.5 volt?
All
Yes
→
Repair the Radiator Fan Relay Output circuit for a short to
voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No
→
Replace the Radiator Fan Relay.
Perform ROAD TEST VERIFICATION - VER-2.
178
DRIVEABILITY - DIESEL
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION —
Continued
Symptom:
*CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR
CALIBRATION
POSSIBLE CAUSES
ECT SENSOR - COLD
ECT SENSOR - HOT
TEST
ACTION
APPLICABILITY
1
NOTE: The thermostat must be operating correctly for this test to be valid.
With the DRB, read and note the engine coolant temperature.
Using a temperature probe, measure the engine block temperature near the ECT
Sensor.
Are the readings within 7°C (13°F) of each other?
All
Yes
→
No
→
Replace the Engine Coolant Temperature Sensor.
Perform ROAD TEST VERIFICATION - VER-2.
2
NOTE: The thermostat must be operating correctly for this test to be valid.
Start the engine.
Using a temperature probe, measure the engine block temperature near the ECT
Sensor. When the engine temperature reaches 75°C (180°F), use the DRB and read
the engine coolant temperature.
Are the readings within 7°C (13°F) of each other?
All
Yes
→
Test Complete.
No
→
Replace the Engine Coolant Temperature Sensor.
Perform ROAD TEST VERIFICATION - VER-2.
179
DRIVEABILITY - DIESEL
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