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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 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 UBEC.

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) between the UBEC and splice pack SP400.
  2. Replace the fuse.

Is the repair complete?

--

Go to Backup Lamp System Check

--

5

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

Is the repair complete?

--

Go to Backup Lamp System Check

--

6

Inspect the B/U LP 25A fuse in the UBEC.

Is the fuse open?

--

Go to Step 7

Go to Step 10

7
  1. Disconnect the backup lamp switch.
  2. Use the J 39200 DMM in order to test for continuity between backup lamp switch terminal C of connector C1 and 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.

Does the J 39200 display the specified value?

B+

Go to Step 17

Go to Step 11

11
  1. Disconnect the harness from the backup lamp switch.
  2. Turn the ignition switch to the RUN position.
  3. Use the J 39200 DMM in order to probe the connector terminal for CKT 839 (PNK) to ground.

Does the J 39200 display the specified value?

B+

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 the backup lamp switch connector terminals of the following circuits:

    • CKT 839 (PNK)
    • CKT 1524 (GRY)

Do the backup lamps light?

--

Go to Step 14

Go to Step 15

14

Replace the backup lamp switch.

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.

Does the J 39200 DMM display the specified value on the hot terminal?

B+

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. Replace the VEH B/U fuse if necessary .
  2. Remove splice pack SP400 from the socket.
  3. Use the J 39200 DMM in order to probe splice pack harness connector terminal C to ground.

Does the J 39200 display the specified value?

B+

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 between the following components:

    • UBEC connector C3, terminal B3
    • Splice pack SP400

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 6

3
  1. Install a new 15A VEH B/U fuse.
  2. Disconnect connector C402.
  3. Remove the left backup lamp bulb.
  4. Use a J 39200 digital multimeter (DMM) in order to probe terminal A (C402) in the harness connector (UBEC side) to ground.

Is the resistance less than the specified value?

2 ohms

Go to Step 4

Go to Step 5

4

Locate and repair the short to ground in CKT 1324 (LT GRN) in one of the following areas:

    • UBEC connector C1, terminal F3 to S309
    • S309 to the Automatic Day/Night Mirror circuit
        Refer to Automatic Day-Night Mirrors Schematics in Stationary Windows.
    • S309 to terminal A of C402
    • S309 to terminal A of C403

Is the repair complete?

--

Go to Backup Lamp System Check

--

5

Important: Inspect the backup lamp bulb for a shorted filament that may cause a short to ground.

Locate and repair a short to ground in CKT 1324 (LT GRN) between terminal A of C402 and the right backup lamp.

Is the repair complete?

--

Go to Backup Lamp System Check

--

6

Inspect the B/U LP fuse in the UBEC.

Is the fuse open?

--

Go to Step 7

Go to Step 10

7
  1. Install a new 25 A B/U LP fuse.
  2. Disconnect the harness from the backup lamp switch.
  3. Use the J 39200 DMM in order to probe the connector terminal for CKT 839 ) (PNK) to ground.

Is continuity present?

--

Go to Step 8

Go to Step 9

8

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

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. Disconnect the harness from the backup lamp switch.
  2. Turn the ignition switch to the RUN position.
  3. Use the J 39200 DMM in order to probe the connector terminal for CKT 839 (PNK) to ground.

Does the J 39200 display the specified value?

B+

Go to Step 12

Go to Step 11

11

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

Is the repair complete?

--

Go to Backup Lamp System Check

--

12

Connect a fused jumper between the backup lamp switch connector terminals for CKT 839 (PNK) and CKT 1524 (GRY).

Do the backup lamps light?

--

Go to Step 13

Go to Step 14

13

Replace the backup lamp switch.

Is the repair complete?

--

Go to Backup Lamp System Check

--

14
  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.

Does the J 39200 DMM display the specified value?

B+

Go to Step 16

Go to Step 15

15

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

Is the repair complete?

--

Go to Backup Lamp System Check

--

16
  1. Replace the VEH B/U fuse if necessary.
  2. Remove one of the backup lamps from the socket.
  3. Use the J 39200 DMM in order to probe the backup lamp socket terminal A to ground.

Does the J 39200 DMM display the specified value?

B+

Go to Step 17

Go to Step 18

17

Locate and repair the open in CKT 1350 and/or CKT 150.

Is the repair complete?

--

Go to Backup Lamp System Check

--

18

Locate and repair the open in CKT 1324.

Is the repair complete?

--

Go to Backup Lamp System Check

--