Schematic Reference: Defogger Schematics

Connector End View Reference: Stationary Windows Connector End Views

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 HVAC Control Assembly.

Does the rear window defogger indicator illuminate?

Go to Step 3

Go to Step 5

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 8

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 20

1. With a scan tool, observe the Rear Defog Switch Input parameter in the Body Control Module (BCM) HVAC data list.
2. Depress the rear window defogger switch.

Does the scan tool display On?

Go to Step 7

Go to Step 6

1. Turn OFF the ignition.
2. Disconnect the harness C4 connector of the BCM.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between battery voltage and the rear defogger switch signal circuit of the HVAC Control Assembly.
5. Depress the rear window defogger switch.

Does the test lamp illuminate?

Go to Step 19

Go to Step 15

1. Turn OFF the ignition.
2. Disconnect the harness C4 connector of the BCM.
3. Turn ON the ignition, with the engine OFF.
4. Connect a 3-ampere fused jumper between battery voltage and the supply voltage circuit of the rear window defogger indicator for the HVAC Control Assembly.

Does the indicator illuminate?

Go to Step 19

Go to Step 16

8

1. Select from the Miscellaneous Test, the Rear Defogger under from the BCM output controls.
2. With a scan tool, command the REAR DEFOG relay ON and OFF.

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

Go to Step 11

Go to Step 9

1. Turn OFF the ignition.
2. Disconnect the REAR DEFOG relay.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the supply voltage circuit and the ground circuit of the REAR DEFOG relay coil.
5. Select from the Miscellaneous Test, the Rear Defogger under from the BCM output controls.
6. With a scan tool, command the REAR DEFOG relay ON.

Does the test lamp illuminate?

Go to Step 17

Go to Step 10

1. Connect a test lamp between the supply voltage circuit of the REAR DEFOG relay coil and a good ground.
2. With a scan tool, command the REAR DEFOG relay ON.

Does the test lamp illuminate?

Go to Step 21

Go to Step 13

1. Turn OFF the ignition.
2. Disconnect the REAR DEFOG relay.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the battery voltage circuit of the REAR DEFOG relay switched input and a good ground.

Does the test lamp illuminate?

Go to Step 12

Go to Step 14

1. Connect a 30 amp fused jumper between the battery voltage circuit of the REAR DEFOG relay switched input and the relay switched output to the supply voltage circuit of the rear defogger.
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 23

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 27

Go to Step 19

Test the battery voltage circuit of the REAR DEFOG relay switched input 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 27

Go to Step 22

Test the rear defogger switch signal circuit of the HVAC Control Assembly for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 18

Test the supply voltage circuit of the rear window defogger indicator for the HVAC Control Assembly 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 27

Go to Step 18

Inspect for poor connections 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 27

Go to Step 24

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 27

Go to Step 25

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 27

Go to Step 26

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

Did you complete the repair?

Go to Step 27

--

Repair an open or high resistance in the ground circuit of the REAR DEFOG relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

--

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

Did you complete the repair?

Go to Step 27

--

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

Did you complete the repair?

Go to Step 27

--

Replace the REAR DEFOG relay.

Did you complete the replacement?

Go to Step 27

--

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 27

--

Important:: Perform the programming or set up procedure for the control module if required.

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

Did you complete the replacement?

Go to Step 27

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2