Schematic Reference: Defogger Schematics

Did you perform the Defogger Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Defogger

1. Start the engine.
2. Depress the rear window defogger switch.
3. Observe the rear window defogger indicator on the Heater and A/C 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 a good 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 in Wiring Systems

Go to Step 19

5

Command the REAR DEFOG relay ON and OFF, by depressing the rear defogger switch on the Heater and A/C 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 a good 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 switch and a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 13

1. Connect a 30 amp fused jumper wire between the battery positive voltage circuit of the REAR DEFOG relay switch and the supply voltage circuit of the rear window defogger grid.
2. Connect a test lamp between the rear window defogger grid and a good 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 a good 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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 15

Test the battery positive voltage circuit of the REAR DEFOG relay switch 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 26

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 18

Inspect for a poor connection at the harness connector of the Heater and A/C 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 26

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 25

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

Did you complete the repair?

Go to Step 26

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

Did you complete the repair?

Go to Step 26

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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 in Wiring Systems.

Did you complete the repair?

Go to Step 26

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Replace the Heater and A/C Control Module. Refer to Control Assembly Replacement in HVAC Systems - Manual.

Did you complete the replacement?

Go to Step 26

--

Important: Perform the setup procedure for the Body Control Module (BCM).

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 26

--

Replace the REAR DEFOG relay.

Did you complete the replacement?

Go to Step 26

--

Replace the Radio Antenna Module. Refer to Radio Antenna Module Replacement in Entertainment.

Did you complete the replacement?

Go to Step 26

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2