2012 Jeep Wrangler JK Factory Service Manual 28 - DTC-Based Diagnostics

P0118-ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT HIGH

P0118-ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT HIGH

For a complete wiring diagram, refer to the Wiring Information.


Theory of Operation

The Engine Coolant Temperature Sensor is located on the left side of the engine block under the Intake Manifold. The Engine Coolant Temperature Sensor operates as a typical two wire sensor. It receives a 5-Volt signal on the (K2) ECT Sensor Signal circuit and shares the (K200) Sensor Ground circuit with the Oil Temperature Sensor. When this fault code is active the EGR system will be disabled.



Possible Causes

(K2) ENGINE COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
(K2) ENGINE COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT OPEN/HIGH RESISTANCE
(K200) ENGINE COOLANT TEMPERATURE SENSOR GROUND CIRCUIT OPEN/HIGH RESISTANCE
ENGINE COOLANT TEMPERATURE SENSOR
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).


1. DTC IS ACTIVE

1. Ignition on, engine not running.
2. With the scan tool, Clear DTCs in the PCM.
3. Monitor the scan tool for at least two minutes.
4. Cycle the ignition key off and on several times, leaving the ignition on for at least 10 seconds at a time.
5. With the scan tool, select View DTCs.


Is the status Active for this DTC?

Yes


No


2. CHECK THE (K2) ENGINE COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the Engine Coolant Temperature Sensor harness connector.
3. Disconnect the PCM C1 harness connector.
4. Remove the ASD Relay from the TIPM.
5. Connect a jumper wire between cavity 30 and cavity 87 of the ASD Relay Connector.
6. Turn the ignition on.
7. Measure the voltage of the (K2) Engine Coolant Temperature Sensor Signal circuit in the Engine Coolant Temperature Sensor harness connector.


Is there any voltage present?

Yes


No


3. CHECK THE (K2) ENGINE COOLANT TEMPERATURE SENSOR SIGNAL FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Remove the jumper wire and install the ASD Relay.
3. Measure the resistance of the (K2) Engine Coolant Temperature Sensor Signal circuit between the Engine Coolant Temperature Sensor harness connector and the PCM C1 harness connector.


Is the resistance below 5.0 Ohms?

Yes


No


4. CHECK THE (K200) SENSOR GROUND CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (K200) Sensor Ground circuit between the Engine Coolant Temperature Sensor harness connector and the PCM C1 harness connector.


Is the resistance below 5.0 Ohms?

Yes


No


5. CHECK THE ENGINE COOLANT TEMPERATURE SENSOR
1. Turn the ignition on.
2. With the scan tool, erase DTCs.
3. Turn the ignition off.
4. Reconnect the PCM C1 harness connector.
5. Connect a jumper wire between the (K200) Sensor Ground circuit and the (K2) Engine Coolant Temperature Sensor Signal circuit in the Engine Coolant Temperature Sensor harness connector.
6. Turn the ignition on.
7. With the scan tool, select View DTCs.


NOTE: The scan tool should display a P0117-Engine Coolant Temperature Sensor Low DTC as active with the jumper wire in place.


Does the scan tool display the DTC as described above?

Yes


No


6. POWERTRAIN CONTROL MODULE

1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Engine Coolant Temperature Sensor and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Perform any Technical Service Bulletins that may apply.


Were any problems found?

Yes


No