GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Jimmy - 4WD 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Backup Lamps Inoperative

Backup Lamps Inoperative Pickup

Step

Action

Value(s)

Yes

No

1

Did you perform the Backup Lights System Check?

--

Go to Step 2

Go to Backup Lamp System Check

2

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

Is the fuse open?

--

Go to Step 3

Go to Step 6

3
  1. Disconnect splice pack SP400 from the wiring harness.
  2. Use a J 39200 digital multimeter (DMM) in order to test for continuity between terminal C in the harness connector and ground.

Is continuity present?

--

Go to Step 4

Go to Step 5

4
  1. Locate and repair the short to ground in CKT 1324 (LT GRN).
  2. Replace the fuse.

Is the repair complete?

--

Go to Backup Lamp System Check

--

5
  1. Locate and repair the short to ground in CKT 1324 (LT GRN) between splice pack SP400 and the backup lamps.
  2. Replace the fuse.

Is the repair complete?

--

Go to Backup Lamp System Check

--

6

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

Is the fuse open?

--

Go to Step 7

Go to Step 10

7
  1. Disconnect the backup lamp switch (M/T) or the park/neutral position switch (A/T).
  2. Use the J 39200 DMM in order to test CKT 839 (PNK) to ground.

Is continuity present?

--

Go to Step 8

Go to Step 9

8
  1. Locate and repair the short to ground in CKT 839 (PNK).
  2. Replace the fuse.

Is the repair complete?

--

Go to Backup Lamp System Check

--

9

Locate and repair the short to ground in CKT 1524 (GRY).

Is the repair complete?

--

Go to Backup Lamp System Check

--

10
  1. Turn the ignition to the RUN position.
  2. Shift the transmission to the REVERSE position.
  3. Connect the J 39200 DMM between the VEH B/U 15A fuse and ground.

Is voltage present?

Battery Voltage

Go to Step 17

Go to Step 11

11
  1. Disconnect the harness from the backup lamp switch (M/T) or the park/neutral position switch (A/T).
  2. Turn the ignition switch to the RUN position.
  3. Use the J 39200 DMM in order to probe CKT 839 (PNK) to ground.

Is voltage present?

Battery Voltage

Go to Step 13

Go to Step 12

12

Locate and repair the open in CKT 839 (PNK).

Is the repair complete?

--

Go to Backup Lamp System Check

--

13

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

Do the backup lamps light?

--

Go to Step 14

Go to Step 15

14

Adjust or replace the backup lamp switch (M/T) or the park/neutral position switch (A/T).

Is the repair complete?

--

Go to Backup Lamp System Check

--

15
  1. Remove the VEH B/U fuse.
  2. Use the J 39200 DMM in order to probe the fuse terminals to ground.

Is voltage present?

Battery Voltage

Go to Step 17

Go to Step 16

16

Locate and repair the open in CKT 1524 (GRY).

Is the repair complete?

--

Go to Backup Lamp System Check

--

17
  1. Remove splice pack SP400 from the socket.
  2. Use the J 39200 DMM in order to probe splice pack harness connector terminal C to ground.

Is voltage present?

Battery Voltage

Go to Step 19

Go to Step 20

18

Repair or replace splice pack SP400 as needed.

Is the repair complete?

--

Go to Backup Lamp System Check

--

19
  1. Connect a fused jumper between terminal C and terminal A at the splice pack SP400 harness connector.
  2. Connect a fused jumper between terminal C and terminal B at the splice pack SP400 harness connector.

Do both of the backup lamps light?

--

Go to Step 18

Go to Step 21

20

Locate and repair the open in CKT 1324.

Is the repair complete?

--

Go to Backup Lamp System Check

--

21

Locate and repair the following conditions for each backup lamp:

    • An open in CKT 1324 between the splice pack harness connector and the backup lamp connector
    • Open bulbs
    • open grounds

Is the repair complete?

--

Go to Backup Lamp System Check

--

Backup Lamps Inoperative Utility

Step

Action

Value(s)

Yes

No

1

Did you perform the Backup Lights System Check?

--

Go to Step 2

Go to Backup Lamp System Check

2

Inspect the VEH B/U 15A fuse in the underhood fuse block.

Is the fuse open?

--

Go to Step 3

Go to Step 4

3

Locate and repair the short to ground in CKT 1324 (LT GRN).

Is the repair complete?

--

Go to Backup Lamp System Check

--

4

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

Is the fuse open?

--

Go to Step 5

Go to Step 8

5
  1. Install a new 25 A B/U LP fuse.
  2. Disconnect the harness from the backup lamp switch (M/T) or the park/neutral position switch (A/T).
  3. Use the J 39200 digital multimeter (DMM) in order to probe CKT 839 (PNK) to ground.

Is continuity present?

--

Go to Step 6

Go to Step 7

6

Locate and repair the short to ground in CKT 839 (PNK).

Is the repair complete?

--

Go to Backup Lamp System Check

--

7

Locate and repair the short to ground in CKT 1524 (GRY).

Is the repair complete?

--

Go to Backup Lamp System Check

--

8
  1. Disconnect the harness from the backup lamp switch (M/T) or the park/neutral position switch (A/T).
  2. Turn the ignition switch to the RUN position.
  3. Use the J 39200 DMM in order to probe CKT 839 (PNK) to ground.

Is voltage present?

Battery Voltage

Go to Step 10

Go to Step 9

9

Locate and repair the open in CKT 839 (PNK).

Is the repair complete?

--

Go to Backup Lamp System Check

--

10

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

Do the backup lamps light?

--

Go to Step 11

Go to Step 12

11

Replace or adjust the backup lamp switch (M/T) or the park/neutral position switch (A/T).

Is the repair complete?

--

Go to Backup Lamp System Check

--

12
  1. Turn the ignition switch to the RUN position.
  2. Shift the transmission to the REVERSE position.
  3. Use the J 39200 DMM in order to probe the VEH B/U 15A fuse to ground.

Is voltage present?

Battery Voltage

Go to Step 14

Go to Step 13

13

Locate and repair the open in CKT 1524 (GRY).

Is the repair complete?

--

Go to Backup Lamp System Check

--

14
  1. Remove one of the backup lamps from the socket.
  2. Use the J 39200 DMM in order to probe the backup lamp socket terminal A to ground.

Is voltage present?

Battery Voltage

Go to Step 15

Go to Step 16

15

Locate and repair the open in CKT 1350.

Is the repair complete?

--

Go to Backup Lamp System Check

--

16

Locate and repair the open in CKT 1324.

Is the repair complete?

--

Go to Backup Lamp System Check

--