Diagnostic Procedures
- Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
- Turn ignition off. Allow engine to cool to ambient air temperature. Turn ignition on, with engine off. Compare ECT sensor parameter to IAT sensor parameter on scan tool. If both parameters are within 2-3 degrees of each other, go to next step. If both parameters are not within 2-3 degrees of each other, go to step 6 .
- Start engine and immediately observe ECT sensor parameter on scan tool. Continue observing ECT for 10 minutes with engine at idle. If ECT indicated on scan tool increases to greater than 68°F (20°C) within 10 minutes, go to step 5 . If ECT indicated on scan tool does not increase to greater than 68°F (20°C) within 10 minutes, go to next step.
- Are there any ECT sensor DTCs set? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to step 8 .
- Fault is not present. Check for any other DTCs. Diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are set, see DIAGNOSTIC AIDS .
- Measure the resistance of the ECT sensor with a Digital Multimeter (DMM). Compare the measured resistance of the ECT sensor with the resistance values. Refer to appropriate SENSOR OPERATING RANGE CHARTS article. Was the resistance of the ECT sensor within specifications? If yes, go to next step. If no, go to step 9 .
- Check for high resistance in ECT sensor circuits. Check for poor connections at PCM and ECT sensor. Repair as necessary. After repairs, go to step 11 . If circuit and connections are okay, go to step 10 .
- Check coolant level or for proper operation of cooling system and thermostat. Repair as necessary. After repairs, go to step 11 .
- Replace ECT sensor. After replacing sensor, go to step 11 .
- Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE under PROGRAMMING. After replacing PCM, go to next step.
- Turn OFF the ignition. Remove the DOME fuse for 30 seconds. Install the DOME fuse. Reset the radio clock time. Start the engine. Operate the vehicle within the Conditions for Running the DTC or until the DTC P0125 diagnostic test has run. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
- Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay.