C0274 Chevrolet TrailBlazer I

The EBCM commands an isolation solenoid ON for 255 consecutive seconds.

Action Taken When the DTC Sets

If equipped, the following actions may occur

1. The EBCM disables the ABS/TCS/DRP.
2. The ABS indicator turns ON.
3. The TRACTION OFF indicator turns ON.
4. The red Brake warning indicator turns ON.
5. The DIC displays the SERVICE BRAKE SYSTEM message.

Conditions for Clearing the DTC

The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Diagnostic Aids

The most likely cause of DTC C0269 or DTC C0274 is a mechanical failure that causes a wheel to lock and remain locked. The DTCs may also set, conceivably, when the ABS is activated on surfaces that are nearly impossible to get traction on. If the DTC sets within these conditions, diagnosis of the ABS system is not necessary.

Test Description

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

1. 2. Performing solenoid tests determines if there is a mechanical malfunction inside the BPMV. Perform dump valve solenoid tests for DTC C0269 or isolation valve solenoid tests for DTC C0274.

Scheme 39

Circuit Description

This DTC identifies a malfunction within the EBCM.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The EBCM detects an internal malfunction.

If equipped, the following actions may occur

1. The EBCM disables the ABS/TCS/DRP.
2. The ABS indicator turns ON.
3. The TRACTION OFF indicator turns ON.
4. The red Brake warning indicator turns ON.
5. The DIC displays the SERVICE BRAKE SYSTEM message.

The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Replace the EBCM if DTC C0273 or DTC C0284 continues to set intermittently.

Scheme 40

The PCM sends engine/axle/tire IDs to the EBCM via serial data communications immediately after the modules are powered up.

The ignition is ON.

The EBCM receives invalid information from the PCM.

If equipped, the following actions occur

1. The EBCM disables the TCS.
2. The traction off indicator turns ON.

The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Diagnose other ABS or TCS related DTCs prior to diagnosing DTC C0279.

If multiple TCS related DTCs are set, or the vehicle being serviced is not equipped with TCS, verify the correct EBCM is installed in the vehicle.

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

1. 3. The PCM must have the correct part number for the specified application.

Scheme 41

The stop lamp switch signal informs the EBCM when the brake pedal is pressed.

Either of the following conditions will cause the DTC to run

1. The ignition is ON and the vehicle achieves at least 56 km/h (35 mph) before coming to a stop.
2. The ignition is ON and the vehicle experiences an ABS event lasting at least 1 second.

The EBCM detects an open or shorted brake switch or brake switch circuit.

This information-only DTC is stored in EBCM memory until it is cleared by using the specified procedure.

The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to TESTING FOR ELECTRICAL INTERMITTENTS , TESTING FOR INTERMITTENT AND POOR CONNECTIONS , WIRING REPAIRS and CONNECTOR REPAIRS in Wiring Systems.

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

1. 4. This step tests for a shorted stoplamp switch.
2. 5. This step tests for an open stoplamp switch.

Scheme 42