Volt

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

The electronic brake control module uses inputs from the electronic brake control brake pedal position sensor to determine when the brake is applied and how much force is used. The electronic brake control module 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 brake pedal travel 1, brake pedal travel 2, 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.

C029C 00

C029C 03, C129A 00, or C129D 00

The electronic brake control module detects voltage below threshold on signal circuit.

C029C 07, C129B 00, or C129E 00

The electronic brake control module detects voltage above threshold on signal circuit.

C029C 1A, C129C 00, or C129F 00

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

C029C 5A, C12B1 00, C12F8 00, or C120C 00

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Note: The 12 V 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. Vehicle in Service Mode with the transmission in PARK.

Note: Do not depress the brake pedal during the Electronic Brake Control Module Learn.

2. Perform the Electronic Brake Control Module Learn procedure with a scan tool.

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

3. Vehicle ON, apply and release the brake pedal.

Note: Vehicle OFF, without applying the brake pedal ensure the brake modulator and high pressure accumulator pressure relief occurs. This process will take approximately 1-3 minutes.

4. Vehicle OFF, without applying the brake pedal.
5. Remove the remote keyless entry transmitter and close all of the vehicle doors. Wait approximately 1-3 minutes until the brake modulator and the high pressure accumulator pressure relief is complete and the vehicle powers down.
6. Vehicle ON, brakes not applied.
7. Verify the scan tool parameters listed below are within the specified range:

•	Brake Controls Brake Pedal Position Sensor 5 V Supply Voltage - Between 4.75-5.25 V.

•	Brake Controls Brake Pedal Position Sensor Circuit 1 - Between 1.4-1.7 V

•	Brake Controls Brake Pedal Position Sensor Circuit 2 - Between 58 78%

⇒	If any parameter is not within the specified range

Refer to Circuit/System Testing.

⇓	If all parameters are within the specified range

8. Vehicle ON, brakes not applied.
9. Verify the scan tool parameters listed below are less the specified range:

•	Brake Master Cylinder Pressure Sensor - Less than 100 kPa (15 psi)

•	Brake Pressure Sensor - Less than 100 kPa (15 psi)

•	High Pressure Accumulator Sensor - Less than 800 kPa (116 psi)

⇒	If any parameter is greater than the specified range

Replace the Q5 brake pressure modulator.

⇓	If all parameters are less than the specified range

10. Perform a brake hydraulic system test, refer to Brake Hydraulic and Assist System Diagnosis .

⇒	If the brake hydraulic system test does not pass

Repair as necessary.

⇓	If the brake hydraulic system tests normal

11. Replace the Q5 brake pressure modulator.
12. 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

13. All OK.

1. Perform the brake hydraulic check, refer to Brake Hydraulic and Assist System Diagnosis .
2. Vehicle OFF, disconnect the harness connector at the B201 brake control brake pedal position sensor.
3. Test for less than 5 Ω between the low reference circuit terminal 1 and ground.

⇒	If 5 Ω or greater

3.1.	Vehicle OFF, disconnect the harness connector at the K17 electronic brake control module.

3.2.	Test for less than 2 Ω in the low reference circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K17 electronic brake control module.

⇓	If less than 5 Ω

4. Vehicle in Service Mode.
5. Test for 4.8-5.2 V between the 5 V reference circuit terminal 5 and ground.

⇒	If less than 4.8 V

5.1.	Vehicle OFF, disconnect the harness connector at the K17 electronic brake control module.

5.2.	Test for infinite resistance between the 5 V reference circuit and ground.

⇒	If less than infinite resistance, repair the short to ground on the circuit.

⇓	If infinite resistance

5.3.	Test for less than 2 Ω in the 5 V reference circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K17 electronic brake control module.

⇒	If greater than 5.2 V

5.1.	Vehicle OFF, disconnect the harness connector at the K17 electronic brake control module, vehicle in service mode.

5.2.	Test for less than 1 V between the 5 V reference circuit and ground.

⇒	If 1 V or greater, repair the short to voltage on the circuit.

⇒	If less than 1 V, replace the K17 electronic brake control module.

⇓	If between 4.8-5.2 V

6. Verify the scan tool Brake Controls Brake Pedal Position Sensor Circuit 1 parameter is less than 1 V.

⇒	If 1 V or greater

6.1.	Vehicle OFF, disconnect the harness connector at the K17 electronic brake control module, vehicle in service mode.

6.2.	Test for less than 1 V between the signal circuit terminal 4 and ground.

⇒	If 1 V or greater, repair the short to voltage on the circuit.

⇒	If less than 1 V, replace the K17 electronic brake control module.

⇓	If less than 1 V

7. Install a 3 A fused jumper wire between the signal circuit terminal 4 and the 5 V reference circuit terminal 5.
8. Verify the scan tool Brake Controls Brake Pedal Position Sensor Circuit 1 parameter is greater than 4.5 V.

⇒	If 4.5 V or less

8.1.	Vehicle OFF, disconnect the harness connector at the K17 electronic brake control module.

8.2.	Test for infinite resistance between the signal circuit terminal 4 and ground.

⇒	If less than infinite resistance, repair the short to ground on the circuit.

⇓	If infinite resistance

8.3.	Test for less than 2 Ω in the signal circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K17 electronic brake control module.

⇓	If greater than 4.5 V

9. Verify the scan tool Brake Controls Brake Pedal Position Sensor Circuit 2 parameter is greater than 80%.

⇒	If 80% or less

9.1.	Vehicle OFF, disconnect the harness connector at the K17 electronic brake control module.

9.2.	Test for infinite resistance between the signal circuit terminal 6 and ground.

⇒	If less than infinite resistance, repair the short to ground on the circuit.

⇒	If infinite resistance, replace the K17 electronic brake control module.

⇓	If greater than 80%

10. Install a 3 A fused jumper wire between the signal circuit terminal 6 and the low reference circuit terminal 1.
11. Verify the scan tool Brake Controls Brake Pedal Position Sensor Circuit 2 is less than 10%.

⇒	If 10% or greater

11.1.

Vehicle OFF, disconnect the harness connector at the K17 electronic brake control module, vehicle in service mode.

11.2.

Test for less than 1 V between the signal circuit terminal 6 and ground.

⇒	If 1 V or greater, repair the short to voltage on the circuit.

⇓	If less than 1 V

11.3.

Vehicle OFF.

11.4.

Test for less than 2 Ω in the signal circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K17 electronic brake control module.

⇓	If less than 10%

12. Replace the B201 brake control brake pedal position sensor.

Perform the Diagnostic Repair Verification after completing the repair.