GM Service Manual Online
For 1990-2009 cars only

Object Number: 393797  Size: MF
ABS Components
Antilock Brake System Schematics
Power Distribution Schematics
Cruise Control Schematics
Exterior Lights Schematics
Handling Electrostatic Discharge Sensitive Parts Notice

Circuit Description

This DTC occurs when internal self-checking safety logic has determined that the Stoplamp Switch is continuously on. This is important because the TCS can not be activated when the Stoplamp Switch is on.

Conditions for Setting the DTC

DTC C1294 can be set if the vehicle speed reaches at least 40 km/h (25 mph). If the brake lamp switch is always on during two consecutive drive cycles, a malfunction exists.

Action Taken When the DTC Sets

    • A malfunction DTC is stored.
    • TCS is disabled.
    • Traction Control indicator is turned on.
    • ABS remains functional.

Conditions for Clearing the DTC

    • Condition for DTC is no longer present and scan tool clear DTC function is used.
    • 100 ignition cycles have passed with no DTCs detected.

Diagnostic Aids

    • Possible causes:
       - Stoplamp switch circuit shorted to voltage.
       - Stoplamp switch misadjusted or shorted.
       - Sticking contacts inside stoplamp switch.
       - Binding pedal.
    • It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.

DTC C1294 Brake Lamp Switch Circuit Always Active

Step

Action

Value(s)

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2

Observe the rear brake lamps.

Are the brake lamps illuminated without pressure applied to the brake pedal?

--

Go to Step 3

Go to Step 4

3

Disconnect the Stoplamp switch connector C1.

Are the brake lamps still illuminated?

--

Go to Step 5

Go to Step 6

4

  1. Disconnect the EBCM/EBTCM harness connector.
  2. Install J 39700 Universal Pinout Box using the J 39700-99 Cable Adapter to the EBCM/EBTCM harness connector only.
  3. Using the DMM, measure the voltage between terminals C7 and D of Universal Pinout Box.

Is any voltage present on CKT 17 without pressure applied to the brake pedal?

--

Go to Step 5

Go to Step 7

5

Repair short to voltage in CKT 17. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

6

Adjust or replace the Stoplamp switch as necessary. Refer to Stop Lamp Switch Adjustment or Stop Lamp Switch Replacement in Hydraulic Brakes.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

7

  1. Reconnect all connectors.
  2. Connect a scan tool to the data link connector.
  3. Select the ABS Data Display.
  4. Carefully drive vehicle for two drive cycles while monitoring the brake input data on the scan tool.

(NOTE: A drive cycle consists of starting the engine, driving above 40 km/h (25 mph) back to 0 km/h (0 mph) and then turning the ignition OFF.)

Was DTC C1294 set in the last two drive cycles?

--

Go to Step 8

--

8

Replace the EBCM/EBTCM. Refer to Electronic Brake Control Module/Electronic Brake and Track Control Module Replacement .

Is the replacement complete?

--

Go to Diagnostic System Check - ABS

--