GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you review the HVAC air delivery operation and perform the necessary inspections?

--

Go to Step 2

Go to Symptoms

2

  1. Start the engine and allow it to reach operating temperature.
  2. Place the front HVAC control module mode switch in the HEAT position.
  3. Place the front auxiliary HVAC control module in the REAR CNTL position.
  4. Place the rear auxiliary HVAC control module in the HI position.
  5. Observe the air flow from the rear auxiliary HVAC unit.
  6. Place the front HVAC control module mode switch in the A/C position.
  7. Listen at the rear auxiliary HVAC module for the rear auxiliary mode valve to move.
  8. Observe the air flow from the rear auxiliary HVAC unit.

Does the rear auxiliary mode valve move and the air temperature change from hot to cold?

--

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Go to Step 3

3

  1. Disconnect the front auxiliary HVAC control module.
  2. Place the ignition switch in the RUN position.
  3. Connect a J 35616-200 unpowered test lamp between front HVAC control module connector cavity G for CKT 341 (BRN) and ground. Refer to Circuit Testing in Wiring Systems.

Did the test lamp light?

--

Go to Step 4

Go to Step 6

4

  1. Disconnect the rear auxiliary temperature valve assembly .
  2. Connect a J 35616-200 unpowered test lamp between rear auxiliary temperature valve assembly connector cavity 10 for CKT 341 (BRN) and ground. Refer to Circuit Testing in Wiring Systems.

Did the test lamp light?

--

Go to Step 5

Go to Step 7

5

Connect a J 39200 digital multimeter (DMM) between rear auxiliary temperature valve assembly connector cavity 10 for CKT 150 (BLK) and ground. Refer to Circuit Testing in Wiring Systems.

Is continuity present?

--

Go to Step 8

Go to Step 9

6

Repair the open in CKT 341 (BRN) between the instrument panel fuse block and the front auxiliary control module.

Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 10

--

7

Repair the open in CKT 341 (BRN) between splice S405 and the instrument panel fuse block.

Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 10

--

8

Replace the front auxiliary HVAC control module.

Refer to Auxiliary Air Conditioning (A/C) Control Assembly Replacement - Front

Is the repair complete?

--

Go to Step 10

--

9

Repair the open in CKT 150 (BLK) between splice S411 and ground G400.

Refer to Wiring Repairs

Is the repair complete?

--

Go to Step 10

--

10

Operate the rear HVAC system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3