C012E
DTC C012E or C12FE
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (with HP2) (Initial Inspection and Diagnostic Overview)Diagnostic System Check - Vehicle (without HP2) (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptors
DTC C012E 00
- Boost Loss Fault
DTC C12FE
- Boost Loss Pressure Loss
Circuit/System Description
The electronic brake control module (EBCM) uses input from the boost pressure sensor for more accurate control during brake and vehicle stability enhancement system (VSES) event. The boost pressure sensor is internal to the brake pressure modulator valve (BPMV). The boost control function will keep operating amongst conditions that cause the boost pressure to be limited to less than commanded. The boost control continues to apply until the boost pressure available is no greater than the MC pressure the driver is applying.
Conditions for Running the DTC
* The ignition is ON.
* Ignition voltage is greater than 10 volts.
* Transmission in Park
Conditions for Setting the DTC
* Boost pressure command greater than boost pressure +1500 kpa (217 psi) for 250 ms.
* Master cylinder pressure greater than boost pressure -200 kpa (29 psi) for 250 ms.
* Accumulator pressure greater than 16,000 kpa (2320 psi) for 250 ms.
* DTCs C12BC, C12BD, C12BE, C128A, C128D, C127D, C12E4, C1255, C1256, C126E, C123C, or C127C not set.
Action Taken When the DTC Sets
* The EBCM disables the ABS/traction control system (TCS)/vehicle stability enhancement system (VSES) for the duration of the ignition cycle.
* A DIC message and/or a warning indicator may be displayed.
Conditions for Clearing the DTC
* The condition for setting 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 (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Verify the 12V battery state of charge is above 12V.
• If the battery state of charge is low, charge the 12V battery. Refer to Battery Charging (Service and Repair).
2. Using the scan tool, perform the EBCM relearn.
3. Start the engine and allow it to idle.
4. Place the transmission in the PARK position.
Note: To ensure the complete brake modulator and high pressure accumulator (HPA) pressure relief procedure is allowed to occur; the brake controller must see one brake pedal apply with the engine running followed by a proper shutdown without applying the brake pedal.
5. Apply and release the brake pedal.
Note: The ignition must transition to the OFF position without pausing at ACCESSORY and without applying the brake pedal. This ensures that the brake modulator and HPA pressure relief occurs. This process will take approximately 1-3 minutes.
6. Turn the ignition OFF without pausing at ACCESSORY and without applying the brake pedal. Remove the key from the ignition.
7. Wait 3 minutes until the brake modulator and HPA pressure relief is complete.
Note: The ignition must remain in the ON position with the engine OFF during this entire procedure.
8. Ignition ON, brakes unapplied, verify the following EBCM scan tool parameters are within the specified values:
* Master Cylinder Pressure Sensor Input -Less than 100 KPA (15 PSI)
* Rear Brake Pressure Sensor -Less than 100 KPA (15 PSI)
* Brake Pressure Sensor Input -Less than 100 KPA (15 PSI)
* Accum. Pressure Sensor -Less than 100 KPA (15 PSI)
• If any of the parameters are not within the specified range, replace the EBCM.
9. Brakes unapplied, verify the following EBCM scan tool parameters are within the specified values:
* BMC Prim. Piston Pos. Sen. 5V Reference Position -Between 4.75 V and 5.25 V
* BMC Primary Piston Position Sensor A -Less than.8V
* BMC Primary Piston Position Sensor B -Greater than 4.2V
• If any of the parameters are not within the specified range, refer to DTC C0277, C120C, C129A, C129B, C129D, C129E, C12B1, or C12F8 (C0277)
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Brake Pressure Modulator Valve Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for EBCM replacement, setup, and programming