GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

  1. Turn the ignition switch to the RUN position.
  2. Press and release the rear defogger switch.
  3. Inspect to see if the defogger ON indicator turns on.

Does the defogger ON indicator turn on?

--

Go to Step 2

Go to Step 21

2

  1. Keep the ignition switch in the RUN position.
  2. Press and release the rear defogger switch.
  3. Inspect to see if the following defoggers turn on:
  4. • The rear window defogger.
    • The right side outside rearview mirror defogger.
    • The left side outside rearview mirror defogger.

Do any defoggers turn on?

--

Go to Step 3

Go to Step 10

3

Does the rear window defogger turn on?

--

Go to Step 4

Go to Step 5

4

Are both sideview mirror heaters inoperative?

--

Go to Step 32

Go to Step 27

5

  1. If the rear defogger ON indicator turns off before the test is made, press and release the rear defogger switch again.
  2. Use a test light to backprobe between the rear defogger grid harness connector C 1 terminal A and connector C 2 terminal A .

Does the test light illuminate?

--

Go to Step 6

Go to Step 7

6

Repair or replace the rear defogger grid. Refer to Grid Line Repair in stationary windows.

Is the repair complete?

--

Go to

Defogger System Check

--

7

  1. If the rear defogger ON indicator turns off before the test is made, press and release the rear defogger switch again.
  2. Use a test light to backprobe between the rear defogger grid harness connector C 1 terminal A and ground.

Does the test light illuminate?

--

Go to Step 8

Go to Step 9

8

Repair a poor connection or an open in circuit 450 between the rear defogger grid connector C 2 terminal A and G401.

Is the repair complete?

--

Go to

Defogger System Check

--

9

Repair a poor connection or an open in circuit 293 between S 268 and the rear defogger grid connector C 1 terminal A.

Is the repair complete?

--

Go to

Defogger System Check

--

10

  1. If the rear defogger ON indicator turns off before the test is made, press and release the rear defogger switch again.
  2. Use a test light to backprobe the rear window defogger relay harness connector between terminal C 1 and terminal A 2.

Does the test light illuminate?

--

Go to Step 11

Go to Step 16

11

Use a test light to backprobe the rear window defogger relay harness connector between terminal C2 and ground.

Does the test light illuminate?

--

Go to Step 12

Go to Step 15

12

Use a test light to backprobe the rear window defogger relay harness connector between terminal C 2 and terminal A 1.

Does the test light illuminate?

--

Go to Step 13

Go to Step 14

13

Replace the HVAC control assembly. Refer to Control Assembly Replacement in HVAC - Manual.

Is the repair complete?

--

Go to

Defogger System Check

--

14

Repair a poor connection or an open in circuit 193.

Is the repair complete?

--

Go to

Defogger System Check

--

15

Repair a poor connection or an open in circuit  41 between S 233 and the rear window defogger relay harness connector terminal C 2.

Is the repair complete?

--

Go to

Defogger System Check

--

16

  1. If the rear defogger ON indicator turns off before the test is made, press and release the rear defogger switch again.
  2. Use a test light to backprobe the rear window defogger relay harness connector between terminal C 1 and ground.

Does the test light illuminate?

--

Go to Step 17

Go to Step 18

17

Repair a poor connection or an open in circuit 293 between the rear window defogger relay harness connector terminal A 2 and S 268.

Is the repair complete?

--

Go to

Defogger System Check

--

18

Use a test light to backprobe between B+ and the rear window defogger relay harness connector terminal C 1.

Does the test light illuminate?

--

Go to Step 19

Go to Step 20

19

Repair the short to ground in circuit 1040.

Is the repair complete?

--

Go to

Defogger System Check

--

20

Repair a poor connection or an open in circuit 1040.

Is the repair complete?

--

Go to

Defogger System Check

--

21

Check fuse B3-B4 in the fuse block.

Is the fuse open?

--

Go to Step 22

Go to Step 23

22

Repair the short to ground in circuit 41.

Is the repair complete?

--

Go to

Defogger System Check

--

23

  1. Turn the ignition switch to the RUN position.
  2. Use a test light to backprobe the HVAC control assembly between the following electrical components:
  3. • (C60) The harness connector C 2 terminal C and terminal K .
    • (CJ4) The harness connector terminal C 5 and terminal C 1.

Does the test light illuminate?

--

Go to Step 11

Go to Step 24

24

Use a test light to backprobe between the following electrical components:

    • (C60) The HVAC control assembly harness connector C 2 terminal C and ground
    • (CJ4) The HVAC control assembly harness connector terminal C 5 and ground

Does the test light illuminate?

--

Go to Step 25

Go to Step 26

25

Repair a poor connection or an open in circuit 1450 between the following electrical components:

    • (C60) The HVAC control assembly harness connector C 2 terminal K and G200
    • (CJ4) The HVAC control assembly harness connector C 2 and G200

Is the repair complete?

--

Go to

Defogger System Check

--

26

Repair a poor connection or an open in circuit 41 between the fuse block terminal B 4 and the following electrical components:

    • (C60) The HVAC control assembly harness connector C 2 terminal C
    • (CJ4) The HVAC control assembly harness connector terminal C 5

Is the repair complete?

--

Go to

Defogger System Check

--

27

  1. If the rear defogger ON indicator turns off before the test is completed, press and release the rear defogger switch again.
  2. Use a test light to backprobe the inoperative outside rearview mirror harness connector between terminal D and terminal E .

Is the test light on?

--

Go to Step 28

Go to Step 29

28

Replace the inoperative outside rearview mirror. Refer to Power Mirror Replacement .

Is the repair complete?

--

Go to

Defogger System Check

--

29

  1. If the rear defogger ON indicator turns off before the test is completed, press and release the rear defogger switch again.
  2. Use a test light to backprobe the inoperative outside rearview mirror harness connector between terminal D and ground.

Is the test light on?

--

Go to Step 30

Go to Step 31

30

Repair a poor connection or an open in circuit 750 between the inoperative sideview mirror harness connector terminal E and G303

s the repair complete?

--

Go to

Defogger System Check

--

31

Repair a poor connection or an open in circuit 267 between connector C 200 terminal G 2 and the inoperative outside rearview mirror harness connector terminal D.

Is the repair complete?

--

Go to

Defogger System Check

--

32

Inspect the fuse A5-A6 in the fuse block.

Is the fuse open?

--

Go to Step 33

Go to Step 34

33

Repair a short to ground in circuit 267.

Is the repair complete?

--

Go to

Defogger System Check

--

34

Repair a poor connection or an open in circuit 293 between the fuse block and splice 268.

Is the repair complete?

--

Go to

Defogger System Check

--