GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Lighting Systems Connector End Views or Computer/Integrating Systems Connector End Views in Computer/Integrating Systems

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

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

Is only one backup lamp inoperative?

Go to Step 10

Go to Step 4

4

Is the vehicle equipped with a manual transmission?

Go to Step 5

Go to Step 9

5

  1. Disconnect the backup lamp switch connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Connect a fused jumper wire between the ignition 1 voltage circuit and the backup lamp signal circuit of the backup lamp switch connector.

Do the backup lamps illuminate?

Go to Step 12

Go to Step 6

6

Connect a test lamp between the ignition 1 voltage circuit of the backup lamp switch connector and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 8

7

Connect a test lamp between the backup lamp signal circuit of the body control module (BCM) and a good ground.

Does the test lamp illuminate?

Go to Step 11

Go to Step 15

8

Test the backup lamp signal circuit and the courtesy lamp supply voltage circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 14

9

Use the scan tool to check if there are any codes set in the current or history Powertrain DTC Information.

Are any codes present?

Go to the Diagnostic System Check in the appropriate Transmission Section

Go to Step 11

10

Test the backup lamp supply voltage and ground circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct a condition?

Go to Step 19

Go to Step 16

11

Test the backup lamp supply voltage circuit for an open or high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct a condition?

Go to Step 19

Go to Step 13

12

Inspect for poor connections at the harness connector of the backup lamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 17

13

Inspect for poor connections at the harness connector of the BCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 18

14

Repair the ignition 1 voltage circuit of the backup lamp switch for a high resistance, an open or a short to ground. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

15

Repair the backup lamp signal circuit of the backup lamp switch for a high resistance or an open. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

16

Replace the affected backup lamp bulb.

Did you complete the replacement?

Go to Step 19

--

17

Replace backup lamp switch. Refer to the following:

    •  Backup Lamp Switch Replacement in Manual Transmission - NV 3500
    •  Backup Lamp Switch Replacement in Manual Transmission - NV 4500
    •  Backup Lamp Switch Replacement in Manual Transmission - ZF S6-650

Did you complete the replacement?

Go to Step 19

--

18

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics and Interior Lights Schematics

1

Did you review Blackout (B/O) Lighting Description and Operation?

Go to Step 2

Go to Blackout Lighting Circuit Operation

2

Is only one backup lamp inoperative?

Go to Step 3

Go to Step 4

3

Test the backup lamp supply voltage circuit of the inoperative bulb for high resistance, an open, or a short to ground.

Did you find and correct the condition?

Go to Step 17

Go to Step 5

4

  1. Inspect the condition of the backup lamp fuses.
  2. If the fuse is open, locate and repair the source of the overload and replace fuse.

Go to Step 17

Go to Step 6

5

Test the ground circuit of the inoperative bulb for high resistance or an open.

Did you find and correct the condition?

Go to Step 17

Go to Step 13

6

Connect a test lamp between connector C1 cavity C of the junction block rear lamps and ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 9

7

Connect a test lamp between connector C1 cavity E and ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 13

8

Locate and repair the open or high resistance in the ground circuit.

Did you complete the repair?

Go to Step 17

___

9

Connect a test lamp between cavity 30 of the interrupt relay and ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 11

10

Locate and repair the open in circuit 24.

Did you complete the repair?

Go to Step 17

___

11

Connect a test lamp between cavity 87 of the interrupt relay and ground.

Does the test lamp illuminate?

Go to Step 14

Go to Step 12

12

Connect a test lamp between cavity F of the backup lamp switch and ground.

Does the test lamp illuminate?

Go to Step 15

Go to Step 16

13

Replace the bulbs.

Did you complete the replacement?

Go to Step 17

___

14

Replace the interrupt relay.

Did you complete the replacement?

Go to Step 17

___

15

Locate and repair the open or high resistance in circuit 1524 or 24.

Did you complete the repair?

Go to Step 17

___

16

Replace the backup lamp switch.

Did you complete the replacement?

Go to Step 17

___

17

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2