Jeep Liberty KJ. Manual — part 681
P0115-ENGINE COOLANT TEMP SENSOR SIGNAL VOLTAGE TOO LOW
For a complete wiring diagram Refer to Section 8W
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ENGINE DIESEL DIAG
KJ
•
When Monitored:
With the ignition on.
•
Set Condition:
The Engine Coolant Temperature Sensor signal is below 0.12 volt.
Possible Causes
ECT SENSOR
ECT SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
ECT SENSOR SIGNAL AND GROUND CIRCUITS SHORTED TOGETHER
ENGINE CONTROL MODULE
Diagnostic Test
1.
CHECK FOR ACTIVE DTC
NOTE: If the ECM detects and stores a DTC, the ECM also stores the engine/vehicle operating conditions
under which the DTC was set. Some of these conditions are displayed on the scan tool at the same time the
DTC is displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may
assist when checking for an active DTC.
Turn the ignition on.
With the scan tool, monitor the Engine Coolant Temperature (ECT) Sensor voltage.
Is the ECT Sensor voltage below 0.25 volt?
Yes
>> Go To 2
No
>> Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
2.
ECT SENSOR
Turn the ignition off.
Disconnect the ECT Sensor harness connector.
Turn the ignition on.
With the scan tool, read the ECT Sensor voltage.
Is the voltage above 4.0 volts?
Yes
>> Replace the ECT Sensor in accordance with the Service Information.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
No
>> Go To 3
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ENGINE DIESEL DIAG
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3.
ECT SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the ECT Sensor harness connector.
Measure the resistance between ground and the ECT Sensor Signal cir-
cuit.
Is the resistance above 1000 ohms?
Yes
>> Go To 4
No
>> Repair the ECT Sensor Signal circuit for a short to ground.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
4.
ECT SENSOR SIGNAL AND GROUND CIRCUITS SHORTED TOGETHER
Turn the ignition off.
Measure the resistance between the ECT Sensor Signal circuit and
Sensor Ground circuit.
Is the resistance above 1000 ohms?
Yes
>> Go To 5
No
>> Repair the ECT Sensor Signal and Ground circuits for a
short together.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
5.
ENGINE CONTROL MODULE
If there are no possible causes remaining, view repair.
Repair
Replace and program the Engine Control Module in accordance with the Service Information.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
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ENGINE DIESEL DIAG
KJ
P0128-ENGINE COOLANT TEMP SENSOR ENGINE IS COLD TOO LONG
For a complete wiring diagram Refer to Section 8W
•
When Monitored:
With the engine running.
•
Set Condition:
When the engine temperature is below 34.0°C.
Possible Causes
ENGINE COLD TOO LONG
Diagnostic Test
1.
CHECK COOLING SYSTEM PERFORMANCE
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 correct.
Start the engine.
With the scan tool, set the engine RPM to 1500 and allow the engine to warm up for 10-15 minutes.
With the scan tool, monitor the Engine Coolant Temperature value during the warm up cycle. Make sure the tran-
sition of temperature change is smooth.
Did the engine temperature reach a minimum of 80° C (176° F)?
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 the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
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ENGINE DIESEL DIAG
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