Coolant Temperature Gauge Troubleshooting

Before testing, check the No. 9 (10A) fuse in the under-hood fuse/relay box and the No. 10 (7.5A) fuse in the under-dash fuse/relay box.

1.Start the engine, and check the malfunction indicator lamp (MIL).

Does the MIL come on and stay on?


YES - Troubleshoot the cause of the ECM/PCM DTC, and recheck.

NO - Go to 2.


2.Check for a multiplex control unit DTC.

Is a DTC indicated?


YES - Troubleshooting the cause of the multiplex control unit DTC, and recheck.

NO - Go to 3.

3.Do the communication line check with the self-diagnosis procedure.

Is the word ‘‘Error'' indicated on the odo/trip display?


YES - The gauge cannot receive the signal from the multiplex control unit and the  ECM/ PCM. Check for an open in the GRY/RED wire (gauge connector terminal A1).

NO - Go to 4.


4.Do the gauge drive circuit check with the self-diagnosis procedure.

Does the temperature gauge needle sweep from the minimum position to the maximum, then return to the minimum position?


YES - Go to 5.

NO - Replace the gauge assembly.n


5.Substitute a known-good ECM/PCM, and recheck.

Did the symptom/indication go away?


YES - Replace the  ECM/ PCM.

NO - Substitute a known-good gauge assembly. If the symptom/indication goes away, replace the gauge assembly.n