GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

1

Did you review the stop lamp operation and perform the necessary inspections?

Go to Step 2

Go to Exterior Lighting Systems Description and Operation

2

  1. Depress the brake pedal.
  2. Release the brake pedal.

Do the stop lamps operate normally?

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

Go to Step 3

3

Is only one lamp inoperative?

Go to Step 4

Go to Step 6

4

Test the right or left stop/turn lamp supply voltage circuit for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 5

5

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

Did you find and correct the condition?

Go to Step 26

Go to Step 20

6

  1. Disconnect the stop lamp switch.
  2. Connect a test lamp between the battery positive voltage circuit of the stop lamp switch and a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 7

7

Test the battery positive voltage circuit of the stop lamp switch for high resistance, an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 8

8

Test the stop lamp switch signal circuit of the underhood fuse block a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 19

9

Connect a 3 amp fused jumper wire between the battery positive voltage circuit and the stop lamp switch signal circuit of the stop lamp switch connector.

Do the stop lamps illuminate?

Go to Step 19

Go to Step 10

10

With the brake pedal pressed, test for continuity between the A and B pins of the stop lamp switch. Refer to Testing for Continuity in Wiring Systems.

Is there continuity?

Go to Step 11

Go to Step 19

11

Test the stop lamp switch signal circuit of the underhood fuse block high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 12

12

  1. Disconnect the stop lamp relay.
  2. Connect a 3 amp fused jumper wire between the battery positive voltage circuit and the stop lamp supply circuit of the stop lamp relay connector.

Do the stop lamps illuminate?

Go to Step 13

Go to Step 14

13

Test the ground circuit of the stop lamp relay for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 18

14

Test the ground circuit of the stop lamps between G401 and S411 for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 15

15

  1. Disconnect the turn/hazard switch C266.
  2. Connect a test lamp between the stop lamp supply voltage circuit of C266 and a good ground.

Does the test lamp illuminate?

Go to Step 21

Go to Step 16

16

Test the stop lamp supply voltage circuit of the turn/hazard switch for high resistance, an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 17

17

Test the battery positive voltage circuit of the underhood fuse block for high resistance, an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 26

Go to Step 18

18

Inspect for poor connections at the harness connector of the stop lamp relay. 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 26

Go to Step 22

19

Inspect for poor connections at the harness connector of the stop lamp 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 26

Go to Step 23

20

Inspect for poor connections at the harness connector of the inoperative lamp. 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 26

Go to Step 24

21

Inspect for poor connections at the harness connector of the turn/hazard 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 26

Go to Step 25

22

Replace the stop lamp relay.

Did you complete the replacement?

Go to Step 26

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23

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

Did you complete the replacement?

Go to Step 26

--

24

Replace the inoperative lamp. Refer to Tail/Turn Signal Lamp Replacement .

Did you complete the replacement?

Go to Step 26

--

25

Replace the turn/hazard switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 26

--

26

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3