P0117

P0117-ENGINE COOLANT TEMPERATURE (ECT) SENSOR VOLTAGE TOO LOW

P0117 - Engine Coolant Temperature (ECT) Sensor Voltage Too Low:

WHEN MONITORED
With ignition on and battery voltage greater than 10.4 volts.

SET CONDITION
The circuit voltage to the ECM falls below a calibrated threshold for a certain period of time.

POSSIBLE CAUSES
- Coolant temperature sensor
- Intermittent condition
- (K2) Sensor signal circuit shorted to ground or (K104) return circuit
- Wiring harness shorted
- ECM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. COOLANT TEMPERATURE SENSOR
Turn the ignition off.
Disconnect the Coolant Temp sensor harness connector.
Check connectors - Clean/repair as necessary.
Measure the resistance of the Temp sensor.

Q: Is the resistance between 300 and 90k ohms?

YES: Go To 2
NO: Replace the Coolant Temperature sensor. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

2. INTERMITTENT CONDITION
Reconnect the coolant temp sensor connected.
Turn the ignition on.
With the scan tool, erase DTCs.
With the scan tool, read DTCs.

Q: Did the DTC reset?

YES: Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure).
NO: Go To 3

3. (K2) SENSOR SIGNAL CIRCUIT SHORTED TO GROUND





Turn the ignition off.
Disconnect the ECM harness connector.
Check connectors - Clean/repair as necessary.
Measure the resistance between the engine ground and the (K2) temperature sensor signal circuit at the sensor harness connector.

Q: Is the resistance more than 100 k ohms?

YES: Go To 4
NO: Repair or replace the short harness. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

4. WIRING HARNESS SHORTED





Measure the resistance between the (K2) signal circuit and all other circuits at the ECM harness connector.

Q: Is the resistance more than 100k ohms?

YES: Go To 5
NO: Repair or replace shorted wiring harness. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

5. ECM
Reconnect the ECM harness connectors.
Turn the ignition on.
With the scan tool, erase DTCs.
While monitoring the scan tool, Disconnect the temperature sensor harness connector.

Q: Did the DTC P0118 set?

YES: Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure).
NO: Replace the ECM. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1