GM Service Manual Online
For 1990-2009 cars only

Backup Lamps Inoperative Pickup

Step

Action

Value(s)

Yes

No

1

Did you perform the Lighting Systems Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Verify that the backup lamps are inoperative.

Do the backup lamps operate normally?

--

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

Go to Step 3

3

Inspect the VEH B/U fuse in the underhood fuse block.

Is the fuse open?

--

Go to Step 4

Go to Step 5

4

  1. Inspect and replace any B/U lamp bulb or socket that is shorted internally.
  2. If no bulb/socket problem is found, locate and repair short to ground in CKT 1324 (LT GRN). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 18

--

5

Inspect the B/U LP 25A fuse in the underhood fuse block.

Is the fuse open?

--

Go to Step 6

Go to Step 9

6

Disconnect the backup lamp switch (M/T) or the park/neutral position switch (A/T) and use the J 39200 Digital Multimeter (DMM) to test for continuity to ground in CKT 839 (PNK). Refer to Circuit Testing in Wiring Systems.

Is continuity present?

--

Go to Step 7

Go to Step 8

7

Locate and repair the short to ground in CKT 839 (PNK). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 18

--

8

Locate and repair the short to ground in CKT 1524 (GRY). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 18

--

9

  1. With the engine off, turn the ignition to the RUN position.
  2. Set the parking brake and block the wheels.
  3. Shift the transmission to the REVERSE position.
  4. Connect the J 39200 DMM between the VEH B/U 15A fuse and ground. Refer to Circuit Testing in Wiring Systems.

Is voltage present?

B+

Go to Step 14

Go to Step 10

10

Disconnect the harness from the backup lamp switch (M/T) or the park/neutral position switch (A/T) and use the J 39200 DMM to check CKT 839 (PNK) for voltage. Refer to Circuit Testing in Wiring Systems.

Is voltage present?

B+

Go to Step 12

Go to Step 11

11

Locate and repair the open or high resistance in CKT 839 (PNK). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 18

--

12

Connect a fused jumper between CKT 839 (PNK) and CKT 1524 (GRY).

Do the backup lamps light?

--

Go to Step 13

Go to Step 17

13

Adjust or replace the backup lamp switch (M/T) or the park/neutral position switch (A/T). Refer to Park/Neutral Position Switch Adjustment or Park/Neutral Position Switch Replacement in Automatic Transmission.

Is the repair complete?

--

Go to Step 18

--

14

Use the J 39200 DMM to test for continuity to ground in CKT 150 (BLK) at either B/U lamp socket. Refer to Circuit Testing in Wiring Systems.

Is continuity present?

--

Go to Step 15

Go to Step 16

15

Locate and repair open or high resistance in CKT 1324 (LT GRN). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 18

--

16

Locate and repair open or high resistance in CKT 1350 (BLK). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 18

--

17

Locate and repair the open or high resistance in CKT 1524 (GRY). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 18

--

18

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3

Backup Lamps Inoperative Utility

Step

Action

Value(s)

Yes

No

1

Did you perform the Lighting Systems Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Verify that the backup lamps are inoperative.

Do the backup lamps operate normally?

--

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

Go to Step 3

3

Inspect the VEH B/U fuse in the underhood fuse block.

Is the fuse open?

--

Go to Step 4

Go to Step 5

4

  1. Inspect and replace any B/U lamp bulb or socket that is shorted internally.
  2. If no bulb/socket problem is found, locate and repair short to ground in CKT 1324 (LT GRN). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 16

--

5

Inspect the B/U LP 25A fuse in the underhood fuse block.

Is the fuse open?

--

Go to Step 6

Go to Step 9

6

Disconnect the backup lamp switch (M/T) or the park/neutral position switch (A/T) and use the J 39200 Digital Multimeter (DMM) to test for continuity to ground in CKT 839 (PNK). Refer to Circuit Testing in Wiring Systems.

Is continuity present?

--

Go to Step 7

Go to Step 8

7

Locate and repair the short to ground in CKT 839 (PNK). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 16

--

8

Locate and repair the short to ground in CKT 1524 (GRY). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 16

--

9

  1. With the engine off, turn the ignition to the RUN position.
  2. Set the parking brake and block the wheels.
  3. Shift the transmission to the REVERSE position.
  4. Connect the J 39200 DMM between the VEH B/U 15A fuse and ground. Refer to Circuit Testing in Wiring Systems.

Is voltage present?

B+

Go to Step 14

Go to Step 10

10

Disconnect the harness from the backup lamp switch (M/T) or the park/neutral position switch (A/T) and use the J 39200 DMM to check CKT 839 (PNK) for voltage. Refer to Circuit Testing in Wiring Systems.

Is voltage present?

B+

Go to Step 12

Go to Step 11

11

Locate and repair the open in CKT 839 (PNK). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 16

--

12

Reinstall the backup lamp bulbs and connect a fused jumper between CKT 839 (PNK) and CKT 1524 (GRY).

Do the backup lamps light?

--

Go to Step 13

Go to Step 15

13

Adjust or replace the backup lamp switch (M/T) or the park/neutral position switch (A/T). Refer to Park/Neutral Position Switch Adjustment or Park/Neutral Position Switch Replacement in Automatic Transmission.

Is the repair complete?

--

Go to Step 16

--

14

Locate and repair open in CKT 1324 (LT GRN). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 16

--

15

Locate and repair the open in CKT 1524 (GRY). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 16

--

16

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3