Defogger Inoperative - Rear Window

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

Step	Action	Yes	No
Schematic Reference: Defogger Schematics Connector End View Reference: Stationary Windows Connector End Views
1	Did you perform the Defogger Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - Defogger
2	Turn ON the ignition, with the engine OFF. Depress the rear window defogger switch. Observe the rear window defogger indicator on the HVAC Control Module. Does the indicator illuminate?	Go to Step 3	Go to Step 8
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 CONDITIONS AND POOR CONNECTIONS in Wiring Systems	Go to Step 10
5	Turn OFF the ignition. Disconnect the harness connector C1 of the Liftgate Module (LGM). Turn ON the ignition, with the engine OFF. Connect a test lamp between the battery positive voltage circuit, terminal A, of the LGM and a good ground. Does the test lamp illuminate?	Go to Step 6	Go to Step 7
6	Test the supply voltage circuit of the rear window defogger for an open or high resistance. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 9
7	Test the battery positive voltage circuit of the LGM for an open or short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 11
8	Inspect for poor connection at the harness connector of the HVAC Control Module. Refer to TESTING FOR INTERMITTENT CONDITIONS AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 12
9	Inspect for poor connections at the harness connector of the LGM. Refer to TESTING FOR INTERMITTENT CONDITIONS AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 13
10	Repair an open or a high resistance in the ground circuit of the rear window defogger. Refer to WIRING REPAIRS in Wiring Systems. Did you find and correct the condition?	Go to Step 14	-
11	Repair a short to ground in the supply voltage circuit of the rear window defogger. Refer to WIRING REPAIRS in Wiring Systems. Did you find and correct the condition?	Go to Step 14	-
12	Replace the HVAC Control Module. Refer to HVAC CONTROL MODULE REPLACEMENT in HVAC Systems - Automatic or HVAC CONTROL MODULE REPLACEMENT in HVAC Systems - Manual. Did you complete the replacement?	Go to Step 14	-
13	IMPORTANT: Perform the set up procedure for the LGM. Refer to LIFT GATE CONTROL MODULE PROGRAMMING in Body Rear End. Replace the LGM. Refer to LIFT GATE CONTROL MODULE REPLACEMENT in Body Rear End.Did you complete the replacement?	Go to Step 14	-
14	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 2