Jeep XJ. Manual — part 848
Symptom:
P1281-ENGINE IS COLD TOO LONG
When Monitored and Set Condition:
P1281-ENGINE IS COLD TOO LONG
When Monitored:
The ignition key on, engine running.
Set Condition:
The engine does not warm to 176 deg. F while driving for 20 minutes after
start.
POSSIBLE CAUSES
ENGINE COLD TOO LONG
TEST
ACTION
APPLICABILITY
1
Note: The best way to diagnose this DTC is to allow the vehicle to remain
outside overnight in order to have a completely cold soaked engine.
Note: Extremely cold outside ambient temperatures may cause this DTC to
set.
Verify that the coolant level is not low and correct as necessary.
Start the engine.
With the DRBIII
t, set the engine RPM to 1500 and allow the engine to warm up for
10-15 minutes.
With the DRBIII
t, monitor the ENG COOLANT TMP DEG value during the warm
up cycle. Make sure the transition of temperature change is smooth.
Did the engine temperature reach a minimum of 80° C (176° F)?
All
Yes
→
Test Complete.
No
→
Refer to the Service Information for cooling system performance
diagnosis. The most probable cause is a Thermostat problem.
Also, refer to any related TSBs.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
153
DRIVEABILITY - GAS
Symptom:
P1282-FUEL PUMP RELAY CONTROL CIRCUIT
When Monitored and Set Condition:
P1282-FUEL PUMP RELAY CONTROL CIRCUIT
When Monitored:
With the ignition on and battery voltage above 10.4 volts.
Set Condition:
An open or shorted condition is detected in the fuel pump relay control
circuit.
POSSIBLE CAUSES
FUEL PUMP RELAY WIRING HARNESS OBSERVABLE
FUSED IGNITION SWITCH OUTPUT CIRCUIT OPEN
FUEL PUMP RELAY
FUEL PUMP RELAY CONTROL CIRCUIT OPEN
FUEL PUMP RELAY CONTROL CIRCUIT SHORTED TO GROUND
FUEL PUMP RELAY WIRING HARNESS INTERMITTENT
POWERTRAIN CONTROL MODULE
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRBIII
t, actuate the Fuel Pump Relay.
Is the Fuel Pump Relay clicking?
All
Yes
→
No
→
2
Turn the ignition off.
Using the wiring diagram as a guide, inspect the fuel pump relay wiring and
connectors.
Were any problems found?
All
Yes
→
Repair as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
No
→
3
Turn the ignition on.
With the DRBIII
t, actuate the Fuel Pump Relay.
Wiggle the wiring harness from the Fuel Pump Relay to the PCM while the relay is
actuating.
Did the Relay clicking stop or become irregular when wiggling the wires?
All
Yes
→
Repair Circuit as necessary where wiggling caused clicking to
stop or become irregular.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
No
→
Test Complete.
154
DRIVEABILITY - GAS
TEST
ACTION
APPLICABILITY
4
Turn the ignition off.
Remove the fuel pump relay from the PDC.
Note: Check connectors - Clean/repair as necessary.
Turn the ignition on.
Measure the voltage on the fused ignition switch output circuit in the fuel pump relay
connector.
Is the voltage above 10.0 volts?
All
Yes
→
No
→
Repair the open fused ignition switch output circuit. NOTE:
Check for a blown fuse.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
5
Turn the ignition off.
Remove the fuel pump relay.
Note: Check connectors - Clean/repair as necessary.
Measure the resistance between terminals 1 (85) and 2 (86) of the fuel pump relay.
Is the resistance between 50 and 90 ohms?
All
Yes
→
No
→
Replace the fuel pump relay.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
6
Turn the ignition off.
Remove the fuel pump relay from the PDC.
Disconnect the PCM harness connector(s).
Note: Check connectors - Clean/repair as necessary.
Measure the resistance of the fuel pump relay control circuit between the fuel pump
relay connector and the PCM harness connector.
Is the resistance below 5.0 ohms?
All
Yes
→
No
→
Repair the open fuel pump relay control circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
7
Turn the ignition off.
Remove the fuel pump relay from the PDC.
Disconnect the PCM harness connector(s).
Note: Check connectors - Clean/repair as necessary.
Measure the resistance between ground and the fuel pump relay control circuit.
Is the resistance below 5.0 ohms?
All
Yes
→
Repair the fuel pump relay control circuit for a short to ground.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
No
→
8
If there are no possible causes remaining, view repair.
All
Repair
Replace the Powertrain Control Module.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
155
DRIVEABILITY - GAS
P1282-FUEL PUMP RELAY CONTROL CIRCUIT —
Continued
Symptom:
P1294-TARGET IDLE NOT REACHED
When Monitored and Set Condition:
P1294-TARGET IDLE NOT REACHED
When Monitored:
With the engine idling and in drive, if automatic. There must not be a
MAP sensor trouble code or a throttle position sensor trouble code.
Set Condition:
Engine idle is not within 200 rpm above or 100 rpm below target idle for
14 seconds. Three separate failures are required to set a bad trip. Two bad trips are
required to set the code.
POSSIBLE CAUSES
THROTTLE PLATES/LINKAGE BINDING
VACUUM LEAK
THROTTLE BODY
THROTTLE BODY DIRTY
TEST
ACTION
APPLICABILITY
1
Turn the ignition on.
With the DRBIII
t, read DTC’s.
Is the Good Trip Counter displayed and equal to zero for P-1294?
All
Yes
→
No
→
Test Complete.
2
Turn the ignition off.
Check the throttle plates and linkage for a binding condition.
The throttle linkages must be at idle position. Ensure the throttle plates are fully
closed and against it’s stops.
Is the throttle plate and linkage free from defects?
All
Yes
→
No
→
Repair as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
3
Inspect the Intake Manifold for vacuum leaks.
Inspect the Power Brake Booster for any vacuum leaks.
Inspect the PCV system for proper operation or any vacuum leaks.
Were any problems found?
All
Yes
→
Repair vacuum leak as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 2.
No
→
156
DRIVEABILITY - GAS
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