Schematic Reference: Defogger Schematics

Connector End View Reference: Stationary Windows Connector End Views

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

1. Turn ON the ignition, with the engine OFF.
2. Observe the rear window defogger indicator on the HVAC control assembly.
3. Command the rear window defogger indicator ON and OFF, by depressing the rear window defogger switch.

Does the rear window defogger indicator turn ON and OFF with each command?

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

Go to Step 3

3

1. Install a scan tool.
2. With the scan tool, observe the Rear Defog Switch Input Data parameter in the body control module (BCM) HVAC data list.
3. Depress the rear window defogger switch.

Does the Rear Defog Switch Input Data parameter always display On?

Go to Step 4

Go to Step 5

1. Turn OFF the ignition.
2. Disconnect harness connector C4 of the BCM.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp from the rear window defogger switch signal circuit to battery voltage.

Does the test lamp illuminate?

Go to Step 6

Go to Step 7

1. Turn OFF the ignition.
2. Disconnect harness connector C3 of the BCM.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp from the supply voltage circuit of the REAR DEFOG relay coil to a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 10

Test the rear defogger switch signal circuit of the HVAC control assembly for short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 8

Inspect for poor connections at the harness connector of the BCM. 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 13

Go to Step 11

Inspect for poor connections at the harness connector of the HVAC control assembly. 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 13

Go to Step 12

Repair a short to voltage in the supply voltage circuit of the REAR DEFOG relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

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Repair a short to voltage in the supply voltage circuit of the rear window defogger indicator. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

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Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 13

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Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement in HVAC Systems - Manual.

Did you complete the replacement?

Go to Step 13

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Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2