P0118
P0118-ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT HIGH
For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams. Electrical Diagrams
Theory of Operation
The Engine Coolant Temperature (ECT) Sensor is located near the thermostat housing and is used to measure the engine coolant temperature. The Coolant Temperature Sensor receives 5-volts and a sensor ground from the Engine Control Module (ECM). The ECM 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, battery temperature, intake air temperature and coolant temperature 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, three sensors grouped at one temperature and one outlier. In the case that all four 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 ECM 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 ECM uses a default value for the Coolant Temperature Sensor. The ECM turns off the MIL lamp when the diagnostic runs and passes in 4 consecutive drive cycles.
- When Monitored:
With ignition on and battery voltage greater than 10.4 volts.
- Set Condition:
The circuit voltage to the Engine Control Module (ECM) 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 30 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. (K2) COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
1. Ignition on.
2. Disconnect the Coolant Temperature Sensor harness connector.
3. Measure the voltage of the (K2) Coolant Temperature Sensor 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 5.0 volts?
Yes
- Repair the short to voltage in the (K2) Coolant Temperature Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
No
- Go To 3
3. COOLANT TEMPERATURE SENSOR
1. Turn the ignition off.
NOTE: Check connectors - Clean/repair as necessary.
2. Measure the resistance across the terminals of the Coolant Temperature Sensor.
Is the resistance between 300 and 90k Ohms?
Yes
- Go To 4
No
- Replace the Coolant Temperature Sensor.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
4. (K2) COOLANT TEMPERATURE SENSOR SIGNAL CIRCUIT OPEN
1. Disconnect the ECM C1 harness connector.
2. Measure the resistance of the (K2) Coolant Temperature Sensor Signal circuit between the Coolant Temperature Sensor harness connector and the ECM C1 harness connector.
Is the resistance below 10.0 Ohms?
Yes
- Go To 5
No
- Repair the open or high resistance in the (K2) Coolant Temperature Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
5. (K914) SENSOR RETURN CIRCUIT OPEN
1. Measure the resistance of the (K914) Coolant Temperature Sensor Return circuit between the Coolant Temperature Sensor harness connector and the ECM C1 harness connector.
Is the resistance below 10.0 Ohms?
Yes
- Replace the Engine Control Module (ECM).
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
No
- Repair the open or high resistance in the (K914) Coolant Temperature Sensor Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.