GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 STS 🢒 Body Systems 🢒 Lighting 🢒 Stop Lamps Always On

Diagnostic Aids

Important: The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation .

Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn OFF the ignition.
  2. Disconnect the stop lamp relay. Refer to Relay Replacement .
  3. Turn ON the ignition, with the engine OFF.

Do the stop lamps turn OFF?

Go to Step 3

Go to Step 7

3
  1. Turn OFF the ignition.
  2. Connect a test lamp between the stop lamp switch signal circuit at the coil side of the stop lamp relay and the stop lamp voltage supply circuit at the switch side of the stop lamp relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Press and release the brake pedal.

Does the test lamp turn ON and OFF?

Go to Step 5

Go to Step 4

4

Test the stop lamp switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 6

5

Inspect for poor connections at the stop lamp relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 8

6

Inspect for poor connections at the harness connector of the instrument panel module (IPM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 9

7

Test the stop lamp voltage supply circuit between the tail lamp assembly and the fuse block-right rear for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

--

8

Replace the stop lamp relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 10

--

9

Replace the IPM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 10

--

10

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2