GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you review the rear window defogger circuit description and perform the necessary inspections?

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Go to Step 2

Go to Symptoms

2

Verify that the rear window defoggers are always on.

Does the rear window defogger operate normally?

--

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

Go to Step 3

3

Use the scan tool in order to inspect for any DTCs (electronic climate control only).

Are any DTCs present?

--

Go to the Appropriate DTC

Go to Step 4

4

  1. Disconnect the rear window defogger relay.
  2. Turn the ignition switch to the RUN position.

Does the rear window defogger remain ON?

--

Go to Step 5

Go to Step 8

5

Remove the HTD MIR fuse from the underhood fuse block.

Does the rear window defogger remain ON?

--

Go to Step 7

Go to Step 6

6

Repair the short to B+ in CKT 2267 (ORN) between the underhood fuse block and the LH/RH outside rear view mirror.

Did you complete the repair?

--

Go to Step 13

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7

Repair the short to B+ in CKT 1093 (PPL) between the underhood fuse block and endgate or liftgate rear window defogger grid.

Did you complete the repair?

--

Go to Step 13

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8

Remove the starter relay in the underhood fuse block and substitute for the rear window defogger relay.

Is the rear defogger relay energized?

--

Go to Step 9

Go to Step 10

9

Disconnect the heater and A/C controller connector or the electronic climate control (ECC) module connector.

Is the defogger relay energized?

--

Go to Step 11

Go to Step 12

10

Replace the rear window defogger relay.

Did you complete the repair?

--

Go to Step 13

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11

Repair a short to ground in CKT 193.

Did you complete the repair?

--

Go to Step 13

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12

Replace the heater and A/C controller or the ECC.

Did you complete the repair?

--

Go to Step 13

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13

Operate the system in order to verify the repair.

Did you find and correct the condition?

--

System OK

Go to Step 3