GM Service Manual Online
For 1990-2009 cars only

Circuit Description

DTC C1295 identifies open brake switch circuitry that prevents the brake switch input to the EBCM from changing states while applying the brake. An open brake switch circuit will result in a modified ABS entrance criteria and possibly false settings of excessive wheel speed variation codes (C1225 thru C1228).

Conditions for Running the DTC

This DTC can set anytime that the EBCM is powered.

Conditions for Setting the DTC

The brake switch input voltage is between 2.2 volts and 5.0 volts for 2.0 seconds.

Action Taken When the DTC Sets

ABS remains functional.

Conditions for Clearing the DTC

    • The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
    • 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

Diagnostic Aids

Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:

    • All brake lamps open.
    • Open brake lamp ground.
    • Brake switch input circuit open.
    • The brake switch is misadjusted.
    • An internal EBCM malfunction.

If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. Tests the brake switch input circuit for an open or high resistance.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

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 Symptoms - Lighting Systems in Lighting Systems

3

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Press the brake pedal.
  4. With a scan tool, observe the Brake Switch Status parameter in the ABS data list.

Does the scan tool display that the Brake Switch Status is ON?

Go to Diagnostic Aids

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the brake switch connector.
  3. Disconnect the EBCM connector.
  4. Connect the J 39700 universal pinout box using the J 39700-99 cable adapter to the EBCM harness connector only.
  5. Test the brake switch input circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 5

5

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 7

Go to Step 6

6

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

Did you complete the replacement?

Go to Step 7

--

7

  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