Test Description
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The number below refers to the step number on the diagnostic table.
- 5: Listen for an audible click when the RR DEFOG relay operates. Command both the ON and OFF states of the RR DEFOG relay. Repeat the commands as necessary.
Defogger Inoperative - Rear Window (w/o Cargo Doors)
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Defogger Schematics | |||
| 1 | Did you review the operation of the rear window defogger system and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Stationary Windows |
| 2 |
|
Go to Step 3 | Go to Step 10 |
| 3 | Connect a test lamp between the rear window defogger grid and a good ground. Does the test lamp illuminate? |
Go to Step 4 | Go to Step 5 |
| 4 | Connect a test lamp between the left side of the rear window defogger grid and the right side of the rear window defogger grid. Does the test lamp illuminate? |
Go to TESTING FOR INTERMITTENT AND POOR CONNECTIONS | Go to Step 14 |
| 5 | Command the RR DEFOG relay ON and OFF, by depressing the rear window defogger switch on the HVAC Control Module. Do you hear a click when you command the RR DEFOG relay ON and OFF? |
Go to Step 8 | Go to Step 6 |
| 6 |
|
Go to Step 7 | Go to Step 15 |
| 7 |
|
Go to Step 12 | Go to Step 10 |
| 8 |
|
Go to Step 9 | Go to Step 11 |
| 9 |
|
Go to Step 12 | Go to Step 17 |
| 10 | Test the control circuit of the RR DEFOG relay for an open or short to battery positive voltage. Refer to CIRCUIT TESTING
and WIRING REPAIRS
. Did you find and correct the condition? |
Go to Step 20 | Go to Step 13 |
| 11 | Test the battery positive circuit of the RR DEFOG relay switch for an open or high resistance. Refer to CIRCUIT TESTING
and WIRING REPAIRS
. Did you find and correct the condition? |
Go to Step 20 | Go to Step 16 |
| 12 | Inspect for a poor connection at the RR DEFOG relay. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS
and CONNECTOR REPAIRS
. Did you find and correct the condition? |
Go to Step 20 | Go to Step 18 |
| 13 | Inspect for a poor connection at the harness connector of the HVAC Control Module. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS
and CONNECTOR REPAIRS
. Did you find and correct the condition? |
Go to Step 20 | Go to Step 19 |
| 14 | Repair an open or high resistance in the ground circuit of the rear window defogger grid. Refer to WIRING REPAIRS
. Did you complete the repair? |
Go to Step 20 | - |
| 15 | Repair an open or high resistance in the ignition 1 voltage circuit of the RR DEFOG relay coil. Refer to WIRING REPAIRS
. Did you complete the repair? |
Go to Step 20 | - |
| 16 | Repair the short to ground in the supply voltage circuit of the rear window defogger. Refer to WIRING REPAIRS
. Did you complete the repair? |
Go to Step 20 | - |
| 17 | Repair an open or high resistance in the supply voltage circuit of the rear window defogger. Refer to WIRING REPAIRS
. Did you complete the repair? |
Go to Step 20 | - |
| 18 | Replace the RR DEFOG relay. Did you complete the replacement? |
Go to Step 20 | - |
| 19 | Replace the HVAC Control Module. Refer to HVAC CONTROL ASSEMBLY
for manual HVAC system or HVAC CONTROL MODULE REPLACEMENT
for automatic HVAC system. Did you complete the replacement? |
Go to Step 20 | - |
| 20 | Operate the system in order to verify the repair. Did you correct the condition? |
System OK | Go to Step 2 |