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

Test Description

The number below refers to the step number on the diagnostic table.

  1. Listen for an audible click when the relay operates.

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. Observe the stop lamps.
  2. Press and release the brake pedal.

Do the stop lamps operate properly?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Press and release the brake pedal.

Does the bass relay turn ON and OFF?

Go to Step 4

Go to Step 5

4
  1. Turn OFF the ignition.
  2. Disconnect the bass relay. Refer to Relay Replacement .
  3. Turn ON the ignition, with the engine OFF.

Do the stop lamps turn OFF?

Go to Step 5

Go to Step 7

5
  1. Turn OFF the ignition.
  2. Connect a test lamp between the coil side supply voltage circuit of the bass relay and the control circuit of the bass 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 8

Go to Step 6

6

Test the control circuit of the bass relay for a short ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 9

7

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

Did you find and correct the condition?

Go to Step 12

Go to Step 8

8

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

Did you find and correct the condition?

Go to Step 12

Go to Step 10

9

Inspect for poor connections at the harness connector of the electronic brake control module (EBCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 11

10

Replace the bass relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 12

--

11
  1. Replace the EBCM. Refer to Control Module References for replacement, setup, and programming.
  2. Perform the brake pedal position sensor recalibration procedure. Refer to Brake Pedal Position Sensor Calibration .

Did you complete the replacement?

Go to Step 12

--

12

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2