C121E

DTC C056D, C121C, C121E, C121F, C123A-C1256, C126E-C127C, C12C2-C12DB, C12DE, C12DF, or C12F2-C12F6

Diagnostic Instructions

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

DTC Descriptors
DTC C056D 00
- ECU Hardware Performance

DTC C056D 3C
- ECU Hardware Performance Internal Communications Failure

DTC C056D 59
- ECU Hardware Performance

DTC C121C
- EBCM Internal Communication Error

DTC C121E
- EBCM Malfunction

DTC C121F
- EBCM Unexpected Exception

DTC C123A
- EBCM High End Timer Watchdog

DTC C123B
- EBCM High End Timer Program Overflow

DTC C123C
- EBCM High End Timer RAM Fault

DTC C123D
- EBCM Solenoid Timeout

DTC C123E
- EBCM High End Timer Periodic Interrupt

DTC C123F
- EBCM Serial Peripheral Interface Inoperative

DTC C1255
- Electronic Control Unit Performance

DTC C1256
- Program ROM Checksum Error

DTC C126E
- EBCM Stack Overrun

DTC C126F
- EBCM Serial Peripheral Interface Performance

DTC C127C
- EBCM Self Test Failed

DTC C127E
- EBCM Module High Temperature

DTC C12C2
- ABS Left Front Isolation Solenoid Valve Driver Shorted

DTC C12C5
- ABS Right Front Isolation Solenoid Valve Diver Shorted

DTC C12C6
- ABS Left Rear Isolation Solenoid Valve Circuit Failure

DTC C12C8
- ABS Right Rear Isolation Solenoid Valve Circuit Failure

DTC C12CC
- ABS Left Front Dump Solenoid Valve Driver Shorted

DTC C12CF
- ABS Right Front Dump Solenoid Valve Driver Shorted

DTC C12D0
- ABS Left Rear Dump Solenoid valve Circuit Open

DTC C12D1
- ABS Left Rear Dump Solenoid Valve Circuit Shorted

DTC C12D2
- ABS Left Rear Dump Solenoid Valve Driver Shorted

DTC C12D3
- ABS Right Rear Dump Solenoid Valve Circuit Open

DTC C12D4
- ABS Right Rear Dump Solenoid Valve Circuit Shorted

DTC C12D5
- ABS Right Rear Dump Solenoid Driver Shorted

DTC C12D6
- ABS Base Brake Open Solenoid Circuit Open

DTC C12D7
- ABS Base Brake Open Solenoid Circuit Shorted

DTC C12D8
- ABS Base Brake Open Solenoid Driver Shorted

DTC C12D9
- ABS Base Brake Closed Solenoid Circuit Open

DTC C12DA
- ABS Base Brake Closed Solenoid Circuit Shorted

DTC C12DB
- ABS Base Brake Closed Solenoid Driver Shorted

DTC C12DE
- ABS Proportioning Valve Solenoid Circuit Open

DTC C12DF
- ABS Proportioning Valve Solenoid Driver Shorted

DTC C12F2
- ABS Left Rear Isolation Solenoid Valve Circuit Shorted

DTC C12F3
- ABS Left Rear Isolation Solenoid Circuit Performance

DTC C12F4
- ABS Proportioning Valve Solenoid Performance

DTC C12F5
- ABS Right Rear Isolation Solenoid Circuit Shorted

DTC C12F6
- ABS Right Rear Isolation Solenoid Performance

Circuit/System Description

The electronic brake control module (EBCM) detects an internal malfunction.

Conditions for Running the DTC

* Ignition ON.
* Ignition voltage is greater than 10 volts.

Conditions for Setting the DTC

The EBCM detects an internal malfunction.

Action Taken When the DTC Sets

* The EBCM disables the antilock brake system (ABS), traction control and the vehicle stability enhancement system for the duration of the ignition cycle.
* A driver information center message and/or a warning indicator may be displayed.

Conditions for Clearing the DTC

* The condition for the DTC is no longer present.
* The EBCM clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

Reference Information
Schematic Reference

Antilock Brake System Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

ABS Description and Operation (ABS Hybrid (HP2))
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the EBCM.
2. Test for less than 1 ohm between the ground circuits listed below and ground.

* Terminal 13
* Terminal 38

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuits listed below and ground.

* Terminal 1
* Terminal 25

• If the test lamp does not illuminate, test the appropriate circuit for a short to ground or an open/high resistance.

4. If all circuits test normal, replace the EBCM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Control Module References (Programming and Relearning) for EBCM replacement, programming and setup