DTC Troubleshooting

Control System DTCs

DTC Troubleshooting: P0118

DTC P0118 : ECT Sensor 1 Circuit High Voltage

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information How To Troubleshoot The Fuel And Emissions Systems.

1. Problem verification:

Problem verification
-1. Turn the ignition switch to ON (II).

-2. Check ECT SENSOR 1 in the DATA LIST with the HDS.

Is about -40 °F (-40 °C) or less, or 4.92 V or more indicated?
-YES- The failure is duplicated. Go to step 2.
-NO- Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at ECT sensor 1 and the ECM.

2. ECT sensor 1 check:

ECT sensor 1 check
-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.





-3. Connect terminals A and B with a jumper wire.









-4. Turn the ignition switch to ON (II).

-5. Check ECT SENSOR 1 in the DATA LIST with the HDS.

Is about -40 °F (-40 °C) or less, or 4.92 V or more indicated?
-YES- Go to step 3.
-NO- Replace ECT sensor 1 ECT Sensor 1 Removal and Installation, then do the repair verification.

3. Determine possible failure area (TW line , SG2 line):

Determine possible failure area (TW line , SG2 line)
-1. Turn the ignition switch to LOCK (0).

-2. Remove the jumper wire.

-3. Turn the ignition switch to ON (II).

-4. Measure the voltage between test points 1 and 2.









Is there about 5.0 V?
-YES- Go to step 4.
-NO- Go to step 5.

4. Open wire check (SG2 line):

Open wire check (SG2 line)
-1. Turn the ignition switch to LOCK (0).

-2. Jump the SCS line with the HDS.

-3. Disconnect the following connector.





-4. Check for continuity between test points 1 and 2.









Is there continuity?
-YES- The SG2 wire is OK. Update the ECM ECM/PCM Update if it does not have the latest software, or substitute a known-good ECM Service and Repair, then do the repair verification.
-NO- Repair an open in the SG2 wire between the ECM (B44) and ECT sensor 1, then do the repair verification.

5. Open wire check (TW line):

Open wire check (TW line)
-1. Turn the ignition switch to LOCK (0).

-2. Jump the SCS line with the HDS.

-3. Disconnect the following connector.





-4. Check for continuity between test points 1 and 2.









Is there continuity?
-YES- The TW wire is OK. Update the ECM ECM/PCM Update if it does not have the latest software, or substitute a known-good ECM Service and Repair, then do the repair verification.
-NO- Repair an open in the TW wire between the ECM (B34) and ECT sensor 1, then do the repair verification.

Repair verification:

-1. Turn the ignition switch to LOCK (0).

-2. Reconnect all connectors.

-3. Turn the ignition switch to ON (II).

-4. Reset the ECM with the HDS How To Troubleshoot The Fuel And Emissions Systems.

-5. Do the ECM idle learn procedure. ECM/PCM Idle Learn Procedure

-6. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0118 indicated?
-YES- Check for poor connections or loose terminals at ECT sensor 1 and the ECM. If the ECM was updated, substitute a known-good ECM Service and Repair, then recheck. If the ECM was substituted, go to step 1.
-NO- Troubleshooting is complete. If the ECM was substituted, replace the original ECM Service and Repair. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.