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.