GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Press the brake pedal.

Do all of the stop lamps illuminate?

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

Go to Step 3

3

Verify if only one of the stop lamps is inoperative or all stop lamps are inoperative.

Is only one stop lamp inoperative?

Go to Step 12

Go to Step 4

4

Inspect the STOP LAMP fuse.

Is the fuse open?

Go to Step 5

Go to Step 6

5

Repair a short to ground in one of the following circuits:

    • CKT 140
    • CKT 17

Is the repair complete?

Go to Step 15

--

6

Use a test lamp in order to backprobe the stop lamp switch harness connector C1 between terminal A and ground.

Did the test lamp light?

Go to Step 7

Go to Step 10

7

  1. Use a test lamp in order to backprobe the stop lamp switch harness connector C1 terminal B and ground.
  2. Depress and hold the brake pedal while observing the test lamp.

Did the test lamp light?

Go to Step 8

Go to Step 9

8

  1. Use a test lamp in order to backprobe between the LH tailamp connector  terminal A and ground.
  2. Depress and hold the brake pedal while observing the test lamp.

Does the test lamp light?

Go to Step 14

Go to Step 11

9

Adjust or replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.

Is the repair complete?

Go to Step 15

--

10

Repair the following conditions in CKT 140:

    • A faulty connection
    • An open circuit

Is the repair complete?

Go to Step 15

--

11

Repair the following conditions in CKT 17 between the stoplamp switch and S415:

    • A faulty connection
    • An open circuit

Is the repair complete?

Go to Step 15

--

12

Test for an open or a high resistance in the inoperative stop lamp power supply or ground supply circuit.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

13

Replace the inoperative stop lamp. Refr to Tail Lamp Replacement .

Did you complete the repair?

Go to Step 15

--

14

Repair an open or poor connection at G401

Did you complete the repair?

Go to Step 15

--

15

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2