Service Information

Volt

DTC C056D, C121C-C121F, C123A-C1256, C126E-C127D, C12C2-C12DF, or C12F2-C12F6

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 provide an overview of each diagnostic category.

DTC C056D 00: Electronic Control Unit Hardware Performance Malfunction

DTC C056D 3C: Electronic Control Unit Hardware Performance Internal Communication Malfunction

DTC C121C 00: Electronic Brake Control Module Internal Communication Malfunction

DTC C121D 00: Electronic Brake Control Module Internal Malfunction

DTC C121E 00: Electronic Brake Control Module Malfunction

DTC C121F 00: Electronic Brake Control Module Supervision Software Malfunction

DTC C123A 00: Electronic Brake Control Module RAM Watchdog

DTC C123B 00: Electronic Brake Control Module RAM Program Overflow

DTC C123C 00: Electronic Brake Control Module RAM Malfunction

DTC C123D 00: Electronic Brake Control Module Solenoid Valve Timeout

DTC C123E 00: Electronic Brake Control Module RAM Periodic Interrupt

DTC C123F 00: Electronic Brake Control Module Serial Peripheral Interface Malfunction

DTC C1255 00: Electronic Control Unit Performance

DTC C1256 00: Control Module Programming Checksum Error

DTC C126E 00: Electronic Brake Control Module Supervision Software Malfunction

DTC C126F 00: Electronic Brake Control Module Serial Peripheral Interface Performance

DTC C127A 00: Electronic Brake Control Module RAM Performance

DTC C127B 00: Electronic Brake Control Module Processor Performance

DTC C127C 00: Electronic Brake Control Module Self-Test Malfunction

DTC C127D 00: Electronic Brake Control Module Internal Malfunction

DTC C12C2 00: ABS Left Front Isolation Solenoid Valve Driver Shorted

DTC C12C5 00: ABS Right Front Dump Solenoid Valve Driver Shorted

DTC C12CC 00: ABS Left Front Dump Solenoid Valve Driver Shorted

DTC C12CF 00: ABS Right Front Dump Solenoid Valve Driver Shorted

DTC C12D0 00: ABS Left Rear Dump Solenoid Valve Circuit Open

DTC C12D1 00: ABS Left Rear Dump Solenoid Valve Circuit Shorted

DTC C12D2 00: ABS Left Rear Dump Solenoid Valve Driver Shorted

DTC C12D3 00: ABS Right Rear Dump Solenoid Valve Circuit Open

DTC C12D4 00: ABS Right Rear Dump Solenoid Valve Circuit Shorted

DTC C12D5 00: ABS Right Rear Dump Solenoid Valve Driver Shorted

DTC C12D6 00: ABS Normally Open Base Brake Solenoid Valve Circuit Open

DTC C12D7 00: ABS Normally Open Base Brake Solenoid Valve Circuit Shorted

DTC C12D8 00: ABS Normally Closed Base Brake Solenoid Valve Driver Shorted

DTC C12D9 00: ABS Normally Closed Base Brake Solenoid Valve Circuit Open

DTC C12DA 00: ABS Normally Closed Base Brake Solenoid Valve Circuit Open

DTC C12DB 00: ABS Normally Closed Base Brake Solenoid Valve Driver Shorted

DTC C12DF 00: Dynamic Rear Proportioning Solenoid Valve Driver Shorted

DTC C12F2 00: ABS Left Rear Isolation Solenoid Valve Circuit Shorted

DTC C12F3 00: ABS Left Rear Isolation Solenoid Valve Performance

DTC C12F4 00: Dynamic Rear Proportioning Solenoid Valve Performance

DTC C12F5 00: ABS Right Rear Isolation Solenoid Valve Circuit Shorted

DTC C12F6 00: ABS Right Rear Isolation Solenoid Valve Performance

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
B+ Terminal 1	C0256 04, C12E5 00	C0256 04, C12E5 00	--	--
B+ Terminal 25	C0201 04	C0201 04	--	--
Ground Terminal 13	-	C056D 00, C12DA 00, C12D7 00	--	--
Ground Terminal 38	-	U0129 00, U1833 00	--	--

Circuit/System Description

The electronic brake control module detects an internal malfunction.

Conditions for Running the DTC

•	Vehicle ON or Vehicle in Service Mode.

•	Ignition voltage is between 8-16 V.

Conditions for Setting the DTC

•	An open electronic brake control module ground circuit.

•	The electronic brake control module detects an internal malfunction.

Action Taken When the DTC Sets

•	A driver information centre message and/or a warning indicator may be displayed.

•	The electronic brake control module disables the antilock brake system, traction control and the vehicle stability enhancement system for the duration of the ignition cycle.

Conditions for Clearing the DTC

•	The condition for the DTC is no longer present.

•	The electronic brake control module clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

Reference Information

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

Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the K17 Electronic Brake Control Module. It may take up to 2 min for all vehicle systems to power down.
Test for less than 10 Ω between the ground circuit terminals listed below and ground:

•	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*

Vehicle in Service Mode.
Verify that a test lamp illuminates between the B+ circuit terminals listed below and ground.

•	Terminal 1

•	Terminal 25

⇒	*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 or the short to ground 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 illuminates*

Replace the K17 Electronic Brake Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for electronic brake control module replacement, programming and setup