GM Service Manual Online
For 1990-2009 cars only

Object Number: 393791  Size: MF
ABS Components
Antilock Brake System Schematics
Power Distribution Schematics
Power Distribution Schematics
Handling Electrostatic Discharge Sensitive Parts Notice

Circuit Description

This DTC identifies a malfunction within the EBCM/EBTCM. When the EBCM/EBTCM relay is activated (turned on), voltage is supplied to the valve solenoids and pump motor.

Conditions for Setting the DTC

DTC C1256 is set when an internal EBCM/EBTCM malfunction exists.

Action Taken When the DTC Sets

    • A malfunction DTC is stored.
    • ABS/ETS/TCS is not disabled.
    • ABS/ETS/TCS Indicators are not turned on.

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 cause for DTC C1256 to set is an internal relay problem within the EBCM/EBTCM.

Step

Action

Value(s)

Yes

No

1

Was the Diagnostic System Check performed?

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Go to Step 2

Go to Diagnostic System Check - ABS

2

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the EBCM/EBTCM harness connector.
  3. Check EBCM/EBTCM and harness connector for damaged, pushed out, or miswired terminals.

Was any damage found?

--

Go to Step 3

Go to Step 4

3

Repair as necessary.

Is the repair complete?

--

Go to Step 4

--

4

  1. Reconnect all connectors.
  2. Using a scan tool clear the DTC.
  3. After clearing the code, test drive the vehicle while monitoring ABS data with a scan tool.

Does DTC reset as a current DTC?

--

Go to Step 5

--

5

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

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