GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Park Avenue 🢒 DTC 🢒 DTC C1255 or C1256

Circuit Description

This DTC identifies a malfunction within the electronic brake control module (EBCM).

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC C1255 Loss of Class 2 Communication
    • DTC C1256 EBCM/EBTCM Internal Malfunction

Conditions for Running the DTC

The antilock brake system (ABS) conditions and the braking conditions are normal.

Conditions for Setting the DTC

An internal EBCM malfunction exists.

Action Taken When the DTC Sets

C1255

If equipped, the following actions occur:

    • The EBCM disables the dynamic rear proportioning (DRP)/ABS/traction control system (TCS)/vehicle stability enhancement system (VSES) for the duration of the ignition cycle.
    • The ABS indicator turns ON.
    • The Traction Off indicator turns ON.
    • The red Brake Warning indicator turns ON.
    • The driver information center (DIC) displays the Service Stability System message.
    • The EBCM will also set DTC C1248.
    • For some DTC C1255xx, the EBCM disables the variable effort steering (VES) for the duration of the ignition cycle.
    • For some DTC C1255xx, the EBCM temporarily suspends the tire inflation module (TIM) monitoring function while the DTC is set.

C1256

    • The ABS remains functional.
    • The ABS indicator remains OFF.

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

Diagnostic Aids
    • The scan tool displays 2 additional characters after the DTC. Take note of the 2 character code and any other DTCs that are set. The 2 character code is an engineering aid used in order to determine the cause of the internal malfunction.
    • When the scan tool displays DTC C1255m3, the EBCM has not been programmed. Perform the setup procedure for the EBCM.

Test Description

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

  1. This step determines whether the DTC is current.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool in order to clear the DTCs.
  4. With the scan tool, perform the Automated Test.

Does the DTC reset as a current DTC?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

Replace the electronic brake control module (EBCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 4

--

4
  1. Use the scan tool in order to clear the DTCs.
  2. With the scan tool, perform the Automated Test.

Does the DTC reset?

Go to Step 2

System OK