GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

Schematic Reference: Exterior Lights Schematics

1

Did you review the Exterior Lighting Systems Description and Operation and perform the necessary inspections?

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Go to Step 2

Go to Exterior Lighting Systems Description and Operation

2

Verify that the backup lamps are inoperative.

Do the backup lamps operate normally?

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

Go to Step 3

3

Is only one backup lamp inoperative?

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Go to Step 4

Go to Step 5

4

  1. Inspect the inoperative bulb/socket for an open filament or open/corroded terminals and replace as necessary.
  2. If a bulb/socket problem is not found, repair the open or high resistance in the backup lamp supply voltage circuit or ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 20

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5

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

Is the fuse open?

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Go to Step 6

Go to Step 7

6

  1. Inspect and replace any B/U lamp bulb or socket that is shorted internally.
  2. If a bulb/socket problem is not found, repair the short to ground in the backup lamp supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 20

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7

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

Is the fuse open?

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Go to Step 8

Go to Step 9

8

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 the Ignition 1 Voltage circuit. Refer to Circuit Testing in Wiring Systems.

Is continuity present?

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Go to Step 13

Go to Step 10

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 DMM between the VEH B/U 15A fuse and ground. Refer to Circuit Testing in Wiring Systems.

Is voltage present?

B+

Go to Step 12

Go to Step 14

10

Disconnect the harness from the backup lamp switch (M/T) or the park/neutral position switch (A/T) and use the DMM to check the Ignition 1 Voltage circuit for voltage. Refer to Circuit Testing in Wiring Systems.

Is voltage present?

B+

Go to Step 11

Go to Step 15

11

Reinstall the backup lamp bulbs and connect a fused jumper between the ignition 1 voltage circuit and the backup lamp supply voltage circuit at the backup lamp switch (M/T) or the park/neutral position switch (A/T).

Do the backup lamps illuminate?

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Go to Step 16

Go to Step 19

12

Use the DMM to test the ground circuit at either B/U lamp socket. Refer to Circuit Testing in Wiring Systems.

Is continuity present?

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Go to Step 17

Go to Step 18

13

Repair the short to ground in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 20

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14

Repair the short to ground in the backup lamp supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 20

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15

Repair the open or high resistance in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 20

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16

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 - 4L60-E.

Did you complete the repair?

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Go to Step 20

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17

Repair the open or high resistance in the backup lamp supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 20

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18

Repair the open or high resistance in the ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 20

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19

Repair the open or high resistance in the backup lamp supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 20

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20

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3