P0118

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 (ECT) is located near the thermostat housing and is used to measure the engine coolant temperature. The Engine Coolant Temperature Sensor receives 5-Volts and a sensor ground from the Powertrain Control Module (PCM). The PCM monitors the change in voltage to determine the coolant temperature. There are two parts to this fault code, a key on check and a rationality check. After an eight hour cold soak, at key ON the readings for the Inlet Air Temperature, Intake Air Temperature and Engine Coolant Temperature Sensors are all compared. If the temperatures differ more than a calibrated amount, then the appropriate sensor fault code would be recorded. The key on monitor is disabled for ambient temperatures below 20°F. This monitor looks for all the sensors to be grouped on one temperature or, in the case that the monitor fails, two sensors grouped at one temperature and one outlier. In the case that all three sensor values are distributed over a range of temperatures this diagnostic will not run. A block heater is one possible cause of such a distribution. The PCM rationality check looks at the temperature reading from the sensor over time and ensures that it changes with engine running. If the sensor reading does not change over a calibrated time limit, the fault will be recorded. Both the key-on and rationality portions of this monitor require that the diagnostic fails in two consecutive drive cycles before the MIL lamp is lit. The ETC lamp will also be illuminated. During this time the PCM uses a default value for the Coolant Temperature Sensor. The PCM turns off the MIL lamp when the diagnostic runs and passes in four consecutive drive cycles.

- When Monitored:
With ignition on and battery voltage greater than 10.4 Volts.

- Set Condition:
The circuit voltage to the Powertrain Control Module (PCM) is above a calibrated threshold for a certain period of time.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC
1. Turn the ignition on.
2. With the scan tool, record all Freeze frame data.
3. With the scan tool, erase DTCs.
4. Turn the ignition off for 75 seconds.
5. Turn the ignition on.
6. With the scan tool, read DTCs.

Did the DTC reset?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

2. CHECK THE (K2) ENGINE COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE




1. Ignition on.
2. Disconnect the Coolant Temperature Sensor harness connector.
3. Measure the voltage of the (K2) Engine Coolant Temperature Sensor (ECT) Signal circuit at the sensor harness connector.

NOTE: The voltage should read approximately 5.0 Volts with connector disconnected and key on.

Is the voltage above 5.1 Volts?

Yes

- Repair the (K2) ECT Sensor Signal circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. CHECK THE ENGINE COOLANT TEMPERATURE SENSOR
1. Turn the ignition off.

NOTE: Check connectors - Clean/repair as necessary.

2. Measure the resistance across the terminals of the ECT Sensor.

Is the resistance between 300 and 90k Ohms?

Yes

- Go To 4

No

- Replace the Engine Coolant Temperature Sensor.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK THE (K2) ENGINE COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT FOR AN OPEN/HIGH RESISTANCE




1. Disconnect the PCM C1 harness connector.
2. Measure the resistance of the (K2) ECT Sensor Signal circuit between the ECT Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 5

No

- Repair the (K2) ECT Sensor Signal circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

5. CHECK THE (K914) SENSOR RETURN CIRCUIT FOR AN OPEN/HIGH RESISTANCE




1. Measure the resistance of the (K914) ECT Sensor Return circuit between the ECT Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Replace the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Repair the (K914) ECT Sensor Return circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.