AutoCodes – Generic – C129D

C129D Code - Brake Pedal Position Sensor 4 Circuit Low 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: C129D indicates Brake Pedal Position Sensor 4 Circuit Low 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.

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Code Popularity 1,021

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
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Code C129D 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 C129D - Brake Pedal Position Sensor 4 Circuit Low Input - AutoCodes.com — C129D Code - Brake Pedal Position Sensor 4 Circuit Low Input

What does this mean?

What are the Possible Causes of the DTC C129D?

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 C129D?

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 C129D 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 C129D code?

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Need Help with the Code?

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Information for Specific Makes

C129D Buick — Brake Pedal Position Sensor 4 Circuit Low Input
C129D Cadillac — Brake Pedal Position Sensor 4 Circuit Low Input
C129D Chevrolet — Brake Pedal Position Sensor 4 Circuit Low Input
C129D GMC — Brake Pedal Position Sensor 4 Circuit Low Input

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 C129D Code

1. What are the common symptoms of OBDII code C129D (Brake Pedal Position Sensor 4 Circuit Low Input)?

The common symptoms of this code may include issues with the brake lights, cruise control not functioning properly, and potential stability control system malfunctions.

2. What are the possible causes of OBDII code C129D?

Possible causes of this code include a faulty brake pedal position sensor, damaged wiring or connectors in the brake pedal position sensor circuit, or a problem with the brake control module.

3. How can I diagnose OBDII code C129D?

Diagnosing this code usually involves using a scan tool to retrieve the code and then performing a thorough inspection of the brake pedal position sensor and its related wiring and connectors.

4. Can I still drive my vehicle with OBDII code C129D?

It is not recommended to drive your vehicle with this code present, as it can affect the proper functioning of crucial safety systems like stability control and brake lights.

5. How do I repair OBDII code C129D?

To repair this code, you may need to replace the brake pedal position sensor, repair any damaged wiring or connectors, or reprogram the brake control module, depending on the exact cause of the issue.

6. Will disconnecting the battery reset OBDII code C129D?

Disconnecting the battery may reset the code temporarily, but it is essential to address the underlying issue causing the code to prevent it from reoccurring.

7. How much does it cost to fix OBDII code C129D?

The cost of fixing this code can vary depending on the cause of the issue, the extent of the repair needed, and the labor rates of the repair shop. It is recommended to get a diagnostic and repair estimate from a qualified mechanic.

8. Can a DIY enthusiast fix OBDII code C129D at home?

Depending on your level of mechanical expertise and access to the necessary tools, you may be able to diagnose and repair this code at home. However, it is crucial to ensure you have the proper knowledge and resources before attempting the repair.

9. Are there any recalls related to OBDII code C129D?

Recalls related to this specific OBDII code may vary depending on the make and model of your vehicle. It is recommended to check with the manufacturer or a dealership to see if there are any relevant recalls for your vehicle.

10. How often does OBDII code C129D occur in vehicles?

The occurrence of this specific OBDII code can vary among different vehicle models and manufacturers. If you encounter this code, it is essential to address it promptly to avoid potential safety issues.