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Engine-Codes – GMC – C129D GMC

C129D GMC Code - Brake Pedal Position Sensor 4 Circuit Low Input

Quick Answer

The C129D GMC code indicates a problem with the Brake Pedal Position Sensor 4 Circuit, specifically a low input signal. Common causes include Faulty brake pedal position sensor, Damaged wiring or connectors in the sensor circuit, Corrosion or debris affecting sensor function. 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 GMC indicates Brake Pedal Position Sensor 4 Circuit Low Input.
Common causes
Common causes include Faulty brake pedal position sensor, Damaged wiring or connectors in the sensor circuit, Corrosion or debris affecting sensor function.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 11, 2024
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Code C129D GMC Description

The C129D GMC code indicates a problem with the Brake Pedal Position Sensor 4 Circuit, specifically a low input signal. This sensor is responsible for detecting the position of the brake pedal and sending this information to the vehicle's electronic control module (ECM). When the sensor detects a low input signal, it means that there is an issue with the sensor's ability to accurately measure the brake pedal position. This can have significant implications for the vehicle's performance and safety.

OBDII Code C129D GMC - Brake Pedal Position Sensor 4 Circuit Low Input
C129D GMC Code - Brake Pedal Position Sensor 4 Circuit Low Input

Common Causes of C129D GMC

  1. Faulty brake pedal position sensor
  2. Damaged wiring or connectors in the sensor circuit
  3. Corrosion or debris affecting sensor function
  4. ECM malfunction or communication issues
  5. Impact or physical damage to the sensor or surrounding components

Symptoms of C129D GMC

  1. Illuminated ABS or traction control warning lights on the dashboard
  2. Inconsistent or unresponsive brake pedal feel
  3. Brakes engaging unexpectedly or inconsistently
  4. Decreased fuel efficiency due to braking system inefficiency
  5. Vehicle may not pass emissions tests due to sensor malfunction

How to Fix C129D GMC

  1. Use a diagnostic scanner to retrieve the specific trouble code and confirm the issue with the brake pedal position sensor.
  2. Inspect the sensor, wiring, and connectors for any visible damage or corrosion. Replace any damaged components.
  3. Test the sensor's functionality using a multimeter to ensure it is sending the correct signal to the ECM.
  4. Clear the trouble code from the ECM's memory and test drive the vehicle to verify that the issue has been resolved.
  5. If the problem persists, further diagnostics may be needed to identify any underlying issues with the braking system or ECM.

Cost to Fix C129D GMC

The cost of repairing a Brake Pedal Position Sensor 4 Circuit Low Input issue can vary depending on the specific cause of the problem and the vehicle's make and model. In general, the cost of replacing a faulty brake pedal position sensor ranges from $100 to $300, including parts and labor. However, additional costs may be incurred if there are other underlying issues that need to be addressed. It is advisable to consult with a qualified mechanic or auto repair shop to get an accurate estimate based on the specific circumstances. Keep in mind that diagnostic time and labor rates can vary, so it's recommended to research local rates for a more precise cost estimate.

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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 GMC Code

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

- Common symptoms include issues with the brake lights, cruise control not working, and potential problems with the vehicle's stability control system.

2. What are the possible causes of OBDII code C129D (GMC) indicating a Brake Pedal Position Sensor 4 Circuit Low Input?

- The code may be triggered by a faulty brake pedal position sensor, damaged wiring or connectors, or a problem with the vehicle's electronic control module (ECM).

3. How can I diagnose the cause of OBDII code C129D (GMC) for the Brake Pedal Position Sensor 4 Circuit Low Input?

- Diagnosing this code typically involves checking the brake pedal position sensor's wiring, connectors, and sensor itself for any signs of damage or malfunction using a diagnostic scan tool.

4. Can I continue driving my vehicle with OBDII code C129D (GMC) related to the Brake Pedal Position Sensor 4 Circuit Low Input?

- It is not recommended to drive the vehicle with this code present, as it may affect the proper functioning of crucial safety systems like the brakes and stability control.

5. How can I repair OBDII code C129D (GMC) for the Brake Pedal Position Sensor 4 Circuit Low Input?

- Repairing this code often involves replacing the faulty brake pedal position sensor, repairing any damaged wiring or connectors, and clearing the code with a diagnostic tool.

6. Are there any DIY tips for fixing OBDII code C129D (GMC) related to the Brake Pedal Position Sensor 4 Circuit Low Input?

- While some basic troubleshooting like checking the sensor's wiring connections can be done by DIY enthusiasts, it is recommended to have a professional mechanic diagnose and repair this issue.

7. How much does it cost to repair OBDII code C129D (GMC) indicating a Brake Pedal Position Sensor 4 Circuit Low Input?

- The cost of repair can vary depending on the exact cause of the issue, but it may range from $100 to $300 for parts and labor.

8. Will resetting the OBDII code C129D (GMC) related to the Brake Pedal Position Sensor 4 Circuit Low Input make it go away permanently?

- Resetting the code may temporarily clear it, but if the underlying issue causing the code is not fixed, it is likely to reappear after some time.

9. Can a malfunctioning Brake Pedal Position Sensor cause other problems in the vehicle?

- Yes, a faulty brake pedal position sensor can affect the proper operation of the vehicle's brake lights, cruise control, and stability control systems.

10. How long does it typically take to repair OBDII code C129D (GMC) for the Brake Pedal Position Sensor 4 Circuit Low Input?

- The repair time can vary depending on the extent of the issue and the availability of parts, but it may take anywhere from 1 to 3 hours for a professional mechanic to diagnose and fix the problem.

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