GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

1

Did you perform the Lighting Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Depress the brake pedal.

Does the system operate normally?

Go to Testing for Electrical Intermittents in Wiring Systems

Go to Step 3

3

  1. Turn the ignition OFF.
  2. Disconnect the stop lamp switch.

Do the brake lamps go out?

Go to Step 6

Go to Step 4

4

Remove the CHMSL fuse.

Do the brake lamps go out?

Go to Step 7

Go to Step 5

5

Remove the VEH STOP fuse.

Do the brake lamps go out?

Go to Step 8

Go to Step 9

6

Inspect for poor connections at the harness connector of the switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

7

Repair the short to voltage in the trailer CHMSL supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

--

8

Repair the short to voltage in the stop Lamp switch signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

--

9

Repair the short to voltage in the CHMSL supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

--

10

Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.

Did you complete the replacement?

Go to Step 11

--

11

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3