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DTC C0256, C12E6, or C12E7

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC C0256 04: Valve Relay Primary Circuit Open

DTC C12E6 00: ABS Switch Circuit Open

DTC C0256 0E: Valve Relay Primary Circuit Low Resistance

DTC C12E7 00: ABS Switch Circuit Shorted

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

B+

C0256 04, C12E5 00

C0256 04, C12E5 00

--

--

Ground Terminal 13

-

C056D 00, C12DA 00, C12D7 00

--

--

Ground Terminal 38

-

U0129 00, U1833 00

--

--

Circuit/System Description

Battery positive voltage is supplied to the electronic brake control module at all times through a 60 A fuse located in the under-bonnet fuse block. The electronic brake control module uses this voltage to power the pump motor. The pump motor is an integral part of the brake pressure modulator, while the pump motor relay is integral to the electronic brake control module. The pump motor relay is not engaged during normal system operation. When the antilock brake system or traction control system operation is required the electronic brake control module activates the pump motor relay and turns the pump motor ON.

Conditions for Running the DTC
    • Vehicle ON or Vehicle in Service Mode.
    • The ignition voltage is greater than 10 V.

Conditions for Setting the DTC

C0256 04 or C12E6 00

    • The electronic brake control module detects an open in the B+ circuit.
    • The engine control module detects the antilock brake system switch circuit is open.

C0256 0E or C12E7 00

    • The electronic brake control module detects an internal power switch shorted.
    • The engine control module detects the antilock brake system switch circuit is shorted.

Action Taken When the DTC Sets
    • The ABS indicator turns ON.
    • The red brake indicator turns ON.
    • The traction control/stability control indicator turns ON.
    • The Service Brake Assist and Service StabiliTrak messages are displayed on the driver information centre.
    • The electronic brake control module disables the antilock brake system, the traction control system and the electronic stability program for the duration of the drive cycle.

Conditions for Clearing the DTC
    • The condition for setting the DTC is no longer present.
    • The history DTC will clear after 40 consecutive fault-free drive cycles have occurred.

Reference Information

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing
  1. Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the K17 electronic brake control module. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between each ground circuit terminal listed below and ground:
    3. • Terminal 13
    • Terminal 38
    ⇒If 10 Ω or greater
    2.1. Vehicle OFF.
    2.2. Test for less than 2 Ω in the ground circuit end to end.
    ⇒If 2 Ω or greater, repair the open/high resistance in the circuit.
    ⇒If less than 2 Ω, repair the open/high resistance in the ground connection.
    ⇓   If less than 10 Ω
  3. Vehicle in Service Mode.
  4. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.
    5. ⇒If the test lamp does not illuminate and the circuit fuse is good
    4.1. Vehicle OFF.
    4.2. Test for less than 2 Ω in the B+ circuit end to end.
    ⇒     If 2 Ω or greater, repair the open/high resistance in the circuit.
    ⇒     If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    ⇒If the test lamp does not illuminate and the circuit fuse is open
    4.1. Vehicle OFF.
    4.2. Test for infinite resistance between the B+ circuit and ground.
    ⇒     If less than infinite resistance, repair the short to ground on the circuit.
    ⇒     If infinite resistance, replace the Q5 brake pressure modulator.
    ⇓   If the test lamp illuminates
  5. Replace the K17 electronic brake control module.
  6. Verify the DTC does not set while operating the vehicle under the Conditions for Running the DTC.
    7. ⇒If the DTC sets
        Replace the Q5 brake pressure modulator.
    ⇓   If the DTC does not set
  7. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    •  Electronic Brake Control Module with Brake Pressure Modulator Valve Replacement
    • Control Module References for electronic brake control module replacement, programming and setup
   


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