AutoCodes – GMC – C129B GMC

C129B GMC Code - Brake Pedal Position Sensor 3 Circuit High Input

Quick Answer

The Electronic Brake Control Module (EBCM) uses inputs from the electronic brake control brake pedal position sensor to determine when the brake is applied and how much force is used. Common causes include Faulty Brake Pedal Position Sensor, Brake Pedal Position Sensor harness is open or shorted, Brake Pedal Position Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: C129B GMC indicates Brake Pedal Position Sensor 3 Circuit High Input.
Common causes: Common causes include Faulty Brake Pedal Position Sensor, Brake Pedal Position Sensor harness is open or shorted, Brake Pedal Position Sensor circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 900

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 04, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code C129B GMC Description

The Electronic Brake Control Module (EBCM) 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 driver's 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.

OBDII Code C129B GMC - Brake Pedal Position Sensor 3 Circuit High Input - AutoCodes.com — C129B GMC Code - Brake Pedal Position Sensor 3 Circuit High Input

What does this mean?

What are the Possible Causes of the DTC C129B GMC?

Faulty Brake Pedal Position Sensor
Brake Pedal Position Sensor harness is open or shorted
Brake Pedal Position Sensor circuit poor electrical connection
Faulty Electronic Brake Control Module (EBCM)

How to Fix the DTC C129B GMC?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the C129B GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the C129B GMC code?

Need more information on how to fix the C129B GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the C129B GMC code diagnosed by a professional: Find a repair shop in your area

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about C129B GMC Code

What does the OBDII code C129B mean for my GMC vehicle?

C129B indicates a high input signal from the Brake Pedal Position Sensor 3, which can affect the vehicle's braking system and stability control.

What are the common symptoms of the C129B code?

Common symptoms include warning lights on the dashboard, erratic braking behavior, and possible loss of stability control functions.

What could cause the C129B code to trigger?

Potential causes include a faulty Brake Pedal Position Sensor, damaged wiring or connectors, or issues within the vehicle's electronic control unit (ECU).

How can I diagnose the C129B code?

To diagnose the C129B code, you can use an OBDII scanner to check for other related codes, inspect the wiring and connections to the Brake Pedal Position Sensor, and test the sensor's functionality.

Is it safe to drive with the C129B code?

It's not recommended to drive with the C129B code active, as it can compromise your braking system and overall vehicle safety.

What repair options are available for a C129B code?

Repair options include replacing the Brake Pedal Position Sensor, repairing or replacing damaged wiring, and reprogramming or replacing the ECU if necessary.

How can I clear the C129B code after repairs?

After making the necessary repairs, you can clear the C129B code using an OBDII scanner or by disconnecting the vehicle's battery for a short period.

Can a bad battery cause the C129B code?

Yes, a weak or failing battery can affect the electronic systems in your vehicle, potentially causing false codes like C129B to appear.

What should I do if I keep getting the C129B code after repairs?

If the C129B code persists after repairs, it may be necessary to perform further diagnostics to identify any underlying issues or consult a professional technician for assistance.