Service Information

Volt

DTC C012B or C12B6-C12B8

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 C012B 01: High Pressure Accumulator Pressure Sensor Short to Battery

DTC C12B7 00: ABS High Pressure Accumulator Pressure Sensor Circuit Short to Battery

DTC C012B 06: High Pressure Accumulator Pressure Sensor Low Voltage/Open

DTC C12B6 00: ABS High Pressure Accumulator Pressure Sensor Circuit Open or Short To Ground

DTC C012B 0F: High Pressure Accumulator Pressure Sensor Signal Erratic

DTC C12B8 00: ABS High Pressure Accumulator Pressure Sensor Erratic

Circuit/System Description

The high pressure accumulator is attached to the brake pressure modulator and provides up to 18,000 kPa (2,600 psi) for use when applying the brakes. The electronic brake control module uses input from the high pressure accumulator sensor for more accurate control during braking and vehicle stability enhancement system event.

Conditions for Running the DTC

•	Ignition voltage is greater than 10 V.

•	Vehicle ON or Vehicle in Service Mode.

Conditions for Setting the DTC

C012B 01 or C12B7 00

A short to battery is detected on the sensor signal circuit.

C012B 06 or C12B6 00

A short to ground or open is detected on signal circuit.

C012B 0F or C12B8 00

The signal is erratic and changes to fast.

Actions 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 dynamic rear proportioning, 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

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 Verification

Vehicle in Service Mode.
Perform the Electronic Brake Control Module Learn procedure with a scan tool.
Verify none of the DTCs listed below are set:

•

DTC C012B

•

DTC C12B6

•

DTC C12B7

•

DTC C12B8

⇒	*If any of the DTCs are set*

3.1.	Replace the Q5 brake pressure modulator.

3.2.	Verify the DTC does not set while operating the vehicle under the Conditions for Running the DTC.

⇒	If the DTC sets, replace the K17 electronic brake control module.

⇓	If the DTC does not set

3.3.

All OK.

⇓	*If none of the DTCs are set*

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