GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2003 🢒 Century 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C1291

Circuit Description

The stop lamp switch signal informs the electronic brake control module (EBCM) when the brake pedal is pressed.

Conditions for Running the DTC

The ABS conditions and the braking conditions are normal.

Conditions for Setting the DTC
    • The stop lamp switch remains open for 3 deceleration cycles.
    • A DTC C1291 was set in a previous ignition cycle.

Action Taken When the DTC Sets
    • The EBCM disables the TCS for the duration of the ignition cycle.
    • The Traction Off indicator turns ON.
    • The ABS remains functional.

Conditions for Clearing the DTC
    • The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
    • The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids
    • Diagnose any wheel speed sensor DTCs before continuing with the diagnosis of the DTC.
    • A deceleration cycle consists of the following sequence:
        1. The vehicle speed is greater than 24 km/h (15 mph).
        2. The vehicle decelerates more than 8 km/h/second (5 mph/second) for 2 seconds.
        3. The vehicle speed decelerates to less than 16 km/h (10 mph).
    • Verify proper stop lamp switch operation using the data list of the scan tool. As the brake is applied, the data list displays the stop lamp switch on within 2.54 cm (1 in) of travel.
    • Possible causes of this DTC are the following conditions:
       - An open stop lamp switch
       - The stop lamp switch is misadjusted
       - An open fuse
       - Circuit has a wiring problem, terminal corrosion, or poor connections
       - Erratic wheel speeds

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests the circuit for a change in states.

    2.

  2. Tests for proper operation of the circuit by bypassing the stop lamp switch. If the fuse in the jumper opens when you perform this test, the signal circuit of the stop lamp switch is shorted to ground.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System Connector End Views or Lighting Systems Connector End Views in Lighting Systems

1

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - ABS

2

Press the brake pedal.

Do the brake lamps turn ON?

Go to Step 3

Go to Step 7

3

  1. Press the brake pedal.
  2. With a scan tool, observe the Brake Switch Status parameter in the ABS data list.

Does the Brake Switch Status parameter change state?

Go to Diagnostic Aids

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Inspect the stop lamp switch and adjust and/or calibrate if needed. Refer to Stop Lamp Switch Adjustment in Lighting Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Disconnect the stop lamp switch connector.
  3. Connect a 3 amp fused jumper wire between the battery positive voltage circuit of the stop lamp switch and the signal circuit of the stop lamp switch.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, observe the Brake Switch Status parameter.

Does the scan tool display Applied?

Go to Step 11

Go to Step 6

6

Test the signal circuit of the stop lamp switch for an open between the splice pack of the stop lamp signal circuit and the EBCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 10

7

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

Did you find and correct the condition?

Go to Step 14

Go to Step 8

8

Test the signal circuit of the stop lamp switch for an open between the stop lamp switch and the splice of the stop lamp signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 9

9

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

Did you find and correct the condition?

Go to Step 14

Go to Step 10

10

Inspect for poor connections at the harness connector of the EBCM. 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 14

Go to Step 12

11

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 14

Go to Step 13

12

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Did you complete the repair?

Go to Step 14

--

13

Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Lighting Systems.

Did you complete the repair?

Go to Step 14

--

14
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK