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C029C




DTC C029C, C120C, C129A-C129F, C12B1, or C12F8

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 C029C 00
- Brake Controls Brake Pedal Position Sensor Circuit

DTC C029C 03
- Brake Controls Brake Pedal Position Sensor Circuit Voltage Below Threshold

DTC C129A
- Brake Pedal Position Sensor 3 Circuit Low-A

DTC C129D
- Brake Pedal Position Sensor 4 Circuit Low-B

DTC C029C 07
- Brake Controls Brake Pedal Position Sensor Circuit Voltage Above Threshold

DTC C129B
- Brake Pedal Position Sensor 3 Circuit High-A

DTC C129E
- Brake Pedal Position Sensor 4 Circuit High-B

DTC C029C 1A
- Brake Controls Brake Pedal Position Sensor Circuit Bias Level Out of Range

DTC C129C
- Brake Pedal Position Sensor 3 Circuit Calibration-A

DTC C129F
- Brake Pedal Position Sensor 4 Circuit Calibration-B

DTC C029C 5A
- Brake Controls Brake Pedal Position Sensor Circuit Plausibility Failure

DTC C12B1
- ABS Master Cylinder Pressure Sensor and Brake Pedal Position Sensor Not Plausible

DTC C12F8
- Brake Pedal Position Sensor 3 Not Plausible-A

DTC C120C
- Brake Pedal Position Sensor 4 Not Plausible-B

Diagnostic Fault Information






Circuit/System Description

The electronic brake control module (EBCM) uses input from the electronic brake control brake pedal position sensor to determine when the brake is applied and how much force is used. The EBCM monitors when the drivers foot is on the brake and locks the offset. The offset is locked when 3 out of the 4 inputs indicate the brake pedal is applied. The 4 inputs are Pedal Travel A, Pedal Travel B, Master Cylinder Pressure Sensor, and the brake pedal position sensor. 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.
* Ignition voltage is greater than 10 volts.

Conditions for Setting the DTC

C029C 00
* The EBCM detects improper offset learn, (foot on brake during EBCM relearn).
* The brake pedal position sensor voltage is out of range.

C029C 03, C129A, or C129D

The EBCM detects voltage below threshold on signal circuit.

C029C 07, C129B, or C129E

The EBCM detects voltage above threshold on signal circuit.

C029C 1A, C129C, or C129F

The electronic brake control pedal position sensor relearn procedure has not been performed.

C029C 5A, C12B1, C12F8, or C120C

This EBCM detects the master cylinder pressure is high when electronic brake control pedal position sensor is reading low travel.

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 Hybrid/EV Battery Pack X1 A4
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 brake sensor performance procedure. It is recommended that a charger/maintainer or equivalent be used to maintain proper battery voltage during this procedure.

1. Place the power button in the ON/RUN position.
2. Place the transmission in PARK.

Note: Do not depress the brake pedal during the EBCM relearn.

3. Using a scan tool access the EBCM, Configuration/Reset Functions, EBCM Relearn. The EBCM relearn procedure will verify valve and pressure sensor calibrations are correct.

Note: To ensure the complete brake modulator and high pressure accumulator (HPA) pressure relief procedure is allowed to occur; the brake controller must see 1 pedal apply with the propulsion system enabled, followed by a proper shutdown without applying the brake pedal.

4. Enable the propulsion system.
5. Apply and release the brake pedal.

Note: The power button must be in the OFF position, and without applying the brake pedal to ensure the brake modulator and high pressure accumulator (HPA) pressure relief occurs. This process will take approximately 1-3 minutes.

6. Place the power button in the OFF position, without applying the brake pedal.
7. Remove the remote keyless entry (RKE) transmitter and close all of the vehicle doors.
8. Wait approximately 1-3 minutes until the brake modulator and the high pressure accumulator (HPA) pressure relief is complete.

Note: The power button must remain in the ON/RUN position, with the engine OFF during the remainder of this diagnostic procedure, unless otherwise instructed.

9. Place the power button in the ON position, engine OFF, and do not apply the brake pedal.
10. Using the scan tool, select Data Display for the EBCM, scroll through the data list, select and accept the following:

* Master Cylinder Pressure Sensor
* Rear Brake Pressure Sensor
* Brake Pressure Sensor
* Accumulator Pressure Sensor
* Brake Controls Brake Pedal Position Sensor 5 V Reference
* Brake Controls Brake Pedal Position Sensor Input A
* Brake Controls Brake Pedal Position Sensor Input B

11. Power button ON, engine OFF, brakes not applied, verify the following sensor parameters are within the specified values:

* Brake Controls Brake Pedal Position Sensor 5 V Reference - Between 4.75-5.25 V
* Brake Controls Brake Pedal Position Sensor Input A - Between 0.4-0.8 V
* Brake Controls Brake Pedal Position Sensor Input B - Between 4.2-4.6 V

• If any of the parameters are not within the specified range, refer to Circuit/System Testing.

12. Power button ON, engine OFF, brakes not applied, verify the following sensor 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 800 kPa (116 psi)

• If any of the parameters are not within the specified range, replace the Q5 brake pressure modulator valve.

Circuit/System Testing

1. Perform a hydraulic check, refer to Brake Hydraulic and Assist System Diagnosis Brake Hydraulic and Assist System Diagnosis.
2. Ignition OFF, disconnect the harness connector at the B201 brake control brake pedal position sensor.
3. Verify that a test lamp illuminates between the low reference circuit terminal 1 and B+.

• If the test lamp does not illuminate, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K17 EBCM.

4. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 5 and ground.

• If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K17 EBCM.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K17 EBCM.

5. Verify the scan tool Brake Controls Brake Pedal Position Sensor Input A parameter is less than 1 V.

• If greater than the specified range, test the signal circuit terminal 4 for a short to voltage. If the circuit tests normal, replace the K17 EBCM.

6. Install a 3 A fused jumper wire between the signal circuit terminal 4 and the 5 V reference circuit terminal 5. Verify the scan tool Brake Controls Brake Pedal Position Sensor Input A parameter is greater than 4.5 V.

• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K17 EBCM.

7. Verify the scan tool Brake Controls Brake Pedal Position Sensor Input B parameter is less than 1 V.

• If greater than the specified range, test the signal circuit terminal 6 for a short to voltage. If the circuit tests normal, replace the K17 EBCM.

8. Install a 3 A fused jumper wire between the signal circuit terminal 6 and the 5 V reference circuit terminal 5. Verify the scan tool Brake Controls Brake Pedal Position Sensor Input B is greater than 4.5 V.

• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K17 EBCM.

9. If all circuits test normal, replace the B201 brake control brake pedal position sensor.

Repair Instructions

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

* Electronic Brake Control Position Sensor Replacement Service and Repair
* Electronic Brake Control Module with Brake Pressure Modulator Valve Replacement Electronic Brake Control Module with Brake Pressure Modulator Valve Replacement
* Control Module References Control Module References for EBCM replacement, programming and setup

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