Antilock Brake System - Hybrid

DTC C0299 or C12FF

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 provides an overview of each diagnostic category.

DTC Descriptors
DTC C0299 00
- Brake Booster Performance

DTC C12FF 00
- EBCM Internal Malfunction

DTC C0299 31
- Brake Booster Performance General Checksum Failure

Circuit/System Description

The electronic brake control module (EBCM) uses input from the brake master cylinder piston position sensor and the brake switch to determine when the brake pedal is being applied and with how much force. These inputs are used to determine the driver's braking intent which is used to the control amount of pressure applied to the wheels.

Conditions for Running the DTC

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

Conditions for Setting the DTC

* The brake pedal is sensed as applied for 6 minutes.
* The vehicle speed is greater than 21 km/h (13 mph).

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 [1][2]Antilock Brakes / Traction Control Systems
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 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 Control Module References for scan tool information

Circuit/System Verification

Note: The battery must be able to maintain a charge during this procedure. It is recommended that a charger/maintainer or equivalent be used to maintain proper battery voltage during this procedure.

1. Verify that no other EBCM DTCs are set.

• If DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

2. Ignition ON, engine OFF, using a scan tool access the EBCM, Module Setup screen, and perform the EBCM Relearn. The relearn procedure will verify valve and pressure sensor calibrations are correct.

Note: To ensure the complete brake modulator and high pressure accumulator 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.

3. Transmission in PARK, engine running, 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 high pressure accumulator pressure relief occurs. This process will take approximately 1-2 minutes.

4. Ignition OFF, key removed from the ignition, wait 2 minutes.

Note: The ignition must remain in the ON position with the engine OFF during the following steps.

5. Ignition ON, brake pedal released, verify the following EBCM scan tool parameters are within the specified range:

* BMC Prim. Piston Pos. Sen. 5 V Reference Position - Between 4.75-5.25 V
* BMC Primary Piston Position Sensor A - Between 0.4-0.8 V
* BMC Primary Piston Position Sensor B - Between 4.2-4.6 V

• If any of the parameters are not within the specified range, refer to DTC C0277, C120C, C129A, C129B, C129D, C129E, C12B1, or C12F8 Antilock Brake System - Hybrid.

6. Brakes not applied, verify the following EBCM scan tool parameters are within the specified range:

* 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 800 kPa (116 psi)

• If any of the parameters are not within the specified range, replace the brake pressure modulator valve.

7. Perform a hydraulic check, refer to Brake Hydraulic and Assist System Diagnosis (Two-mode Hybrid) Brake Hydraulic and Assist System Diagnosis (Two-mode Hybrid).

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 Control Module References for EBCM replacement, setup, relearn and programming