P0118-ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT HIGH

For a complete wiring diagram Refer to Section 8W.

When Monitored:
With the ignition on. Battery voltage greater than 10.4 volts.
Set Condition:
The Engine Coolant Temperature (ECT) sensor circuit voltage at the PCM is greater than 4.98 volts for more than 2.8 seconds. One Trip Fault. Three good trips to turn off the MIL. (ETC lamp will illuminate with the MIL if equipped.)

Possible Causes

(K2) ECT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE

(K2) ECT SIGNAL CIRCUIT OPEN

(K900) SENSOR GROUND CIRCUIT OPEN

ECT SENSOR

PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Diagnostic Test

1.ECT SENSOR VOLTAGE ABOVE 4.98 VOLTS

Is the voltage above 4.98 volts?

Yes

Go To 2

Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

2.ECT SENSOR

Is the voltage below 1.0 volt with the jumper wire installed?

Yes

Replace the ECT Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 3
NOTE: Remove the jumper wire before continuing.

3.(K2) ECT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE

Is the voltage above 0 volts?

Yes

Repair the short to battery voltage in the (K2) ECT Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 4

4.(K2) ECT SIGNAL CIRCUIT OPEN

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

Is the resistance below 5.0 ohms?

Yes

Go To 5

Repair the open in the (K2) ECT Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

5.(K900) SENSOR GROUND CIRCUIT OPEN

Is the resistance below 5.0 ohms?

Yes

Go To 6

Repair the open in the (K900) Sensor ground circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

6.PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Were there any problems found?

Yes

Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)