HVAC Control Power, Ground, And Communication Circuit Troubleshooting

HVAC Control Power, Ground, and Communication Circuit Troubleshooting

1. Check the No. 36 (10 A) fuse in the under-dash fuse/ relay box.

Is the fuse OK?

YES -

Go to step 2

NO -

Replace the fuse, and recheck. If the fuse blows again, check for a short in the No. 36 (10 A) fuse circuit.�

2. Turn the ignition switch to ON (II).

3. Measure the voltage between HVAC control unit connector B (16P) terminal No. 15 and body ground.





Is there battery voltage?

YES -

Go to step 4.

NO -

Repair an open in the wire between the No. 36 (10 A) fuse in the under-dash fuse/relay box and the HVAC control unit.�

4. Measure the voltage between HVAC control unit connector B (16P) terminal No. 4 and body ground.





Is there less than 0.5 V?

YES -

Go to step 5.

NO -

Check for an open in the wire between the HVAC control unit and body ground. If the wire is OK, check for poor ground at G403.�

5. Turn the ignition switch to LOCK (0).

6. Disconnect HVAC control unit connector B (16P).

7. Disconnect HVAC control unit connector A (24P).

8. Check for continuity between the following terminals of the gauge control module 32P connector and HVAC control unit connector A (24P).









Is there continuity?

YES -

Check for loose wires or poor connections at HVAC control unit connectors A (24P), and B (16P). If the connections are good, substitute a known-good HVAC control unit, and recheck. If the indication goes away, replace the original HVAC control unit HVAC Control Unit Removal/Installation.�

NO -

Repair an open in the wire between the HVAC control unit and the gauge control module.�