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

Important: Make sure that the park or head lights are turned OFF. The backlighting will effect the illumination of the rear window defogger indicator.

1. Start the engine.
2. Depress the rear window defogger switch.
3. Observe the rear window defogger indicator on the HVAC control module.

Does the rear window defogger indicator illuminate?

Go to Step 3

Go to Step 12

Connect a test lamp between the rear window defogger grid and ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 5

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

Go to Step 19

5

Command the REAR DEFOG relay ON and OFF, by depressing the rear defogger switch on the HVAC control module.

Do you hear a click when you command the REAR DEFOG relay ON and OFF?

Go to Step 8

Go to Step 6

1. Turn OFF the ignition.
2. Disconnect the REAR DEFOG relay.
3. Start the engine.
4. Connect a test lamp between the supply voltage circuit of the REAR DEFOG relay coil and ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 11

1. Connect a test lamp between the supply voltage circuit of the REAR DEFOG relay coil and the control circuit of the REAR DEFOG relay.
2. Depress the rear window defogger switch.

Does the test lamp illuminate?

Go to Step 17

Go to Step 12

1. Turn OFF the ignition.
2. Disconnect the REAR DEFOG relay.
3. Connect a test lamp between the battery positive voltage circuit of the REAR DEFOG relay switched input and ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 13

1. Connect a 30-amp fused wire between the battery positive voltage circuit of the REAR DEFOG relay switched input and the relay switched output to the supply voltage circuit of the rear window defogger grid.
2. Connect a test lamp between the rear window defogger grid and ground.

Does the test lamp illuminate?

Go to Step 17

Go to Step 10

1. Disconnect the harness connector of the radio antenna module.
2. Connect a test lamp between the supply voltage circuit of the rear window defogger grid and ground.

Does the test lamp illuminate?

Go to Step 14

Go to Step 21

Test the supply voltage circuit of the REAR DEFOG relay coil for an open or short to ground. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

Go to Step 25

Go to Step 16

Test the control circuit of the REAR 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 25

Go to Step 15

Test the battery positive voltage circuit of the REAR DEFOG relay switched input for an open or short to ground. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

Go to Step 25

Go to Step 20

Test the supply voltage circuit of the rear window defogger grid between the radio antenna module and the rear window defogger grid for an open or high resistance. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

Go to Step 25

Go to Step 18

Inspect for a poor connection at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

Go to Step 25

Go to Step 22

Inspect for a poor connection at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

Go to Step 25

Go to Step 23

Inspect for a poor connection at the REAR DEFOG relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

Go to Step 25

Go to Step 24

Inspect for a poor connection at the harness connector of the radio antenna module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

Go to Step 25

Go Step 24 to

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 25

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Repair the short to ground in the supply voltage circuit of the rear window defogger grid. Refer to Wiring Repairs.

Did you complete the repair?

Go to Step 25

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Repair an open or high resistance in the supply voltage circuit of the rear window defogger grid. Refer to Wiring Repairs.

Did you complete the repair?

Go to Step 25

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Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 25

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Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 25

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Replace the REAR DEFOG relay. Refer to Relay Replacement.

Did you complete the replacement?

Go to Step 25

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Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2