Coolant Temperature Gauge Circuit 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? 

   YES:  Troubleshoot the cause of the ECM DTC (see SELF-DIAGNOSTICS ), and recheck.

   NO:  Go to step 2.

2. Check for a multiplex control unit DTC (see MULTIPLEX CONTROL SYSTEM ).

   Is a DTC indicated? 

   YES:  Troubleshooting the cause of the multiplex control unit DTC (see MULTIPLEX CONTROL SYSTEM ), and recheck.

   NO:  Go to step 3.

3. Do the communication line check with the self-diagnostic function (see SELF-DIAGNOSTIC FUNCTION  ).

   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. Check for an open in the WHT/GRN wire (gauge connector terminal B13). If no open is found, go to step  5 .

   NO:  Go to step 4.

4. Do the gauge drive circuit check with the self-diagnostic function (see SELF-DIAGNOSTIC FUNCTION  ).

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

   YES:  Go to step 5.

   NO:  Replace the gauge assembly.

5. Substitute a known-good ECM and recheck.

   Did the symptom/indication go away? 

   YES:  Replace the ECM.

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