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Engine-Codes – Generic – P129D

P129D Code - Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage

Quick Answer

The P129D diagnostic trouble code (DTC) refers to a problem with the Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage. Common causes include Faulty fuel pump driver control module, Wiring issues or corroded connections in the circuit, Defective ignition switch. 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
P129D indicates Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage.
Common causes
Common causes include Faulty fuel pump driver control module, Wiring issues or corroded connections in the circuit, Defective ignition switch.
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 07, 2024
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Code P129D Description

The P129D diagnostic trouble code (DTC) refers to a problem with the Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage. This code indicates that the voltage in the circuit related to the fuel pump driver control module is below the acceptable range when the ignition is turned on or during engine startup. The fuel pump driver control module is responsible for regulating the fuel pump operation, ensuring the correct fuel pressure is maintained in the fuel system.

OBDII Code P129D - Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage
P129D Code - Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage

Common Causes of P129D

  1. Faulty fuel pump driver control module
  2. Wiring issues or corroded connections in the circuit
  3. Defective ignition switch
  4. Battery or alternator problems affecting voltage supply
  5. Issues with the fuel pump itself

Symptoms of P129D

  1. Engine misfires or hesitation during acceleration
  2. Difficulty starting the engine or a no-start condition
  3. Decreased fuel efficiency
  4. Illumination of the check engine light
  5. Rough idling or stalling

How to Fix P129D

  1. Perform a thorough inspection of the fuel pump driver control module circuit and wiring to check for any visible damage or corrosion.
  2. Test the ignition switch to ensure it is functioning correctly and supplying the proper voltage to the circuit.
  3. Check the fuel pump driver control module for faults using a diagnostic scanner and replace if necessary.
  4. Test the battery and alternator to ensure they are providing the correct voltage to the fuel pump circuit.
  5. Clear the DTC and reset the vehicle's computer system to see if the issue has been resolved.

Cost to Fix P129D

The typical repair costs for addressing a P129D code can vary depending on the specific cause of the issue and the labor rates at the auto repair shop. In general, the cost of replacing a faulty fuel pump driver control module or repairing wiring issues can range from $200 to $500, including parts and labor. However, additional costs may be incurred if other components need replacement or if further diagnostics are required. It is recommended to consult with a qualified mechanic or repair shop to obtain an accurate estimate based on your vehicle's make and model.

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Code P129D Information for Specific Makes

  • P129D BMW — Manifold Absolute Pressure Maximum Pressure Implausible
  • P129D Buick — Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage
  • P129D Cadillac — Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage
  • P129D Chevrolet — Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage
  • P129D GMC — Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage
  • P129D MINI — Manifold Absolute Pressure Maximum Pressure Implausible
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 P129D Code

1. What are the common symptoms of OBDII code P129D?

- Common symptoms include difficulty starting the vehicle, engine stalling, rough idling, and a noticeable decrease in fuel efficiency.

2. What can cause the Fuel Pump Driver Control Module Ignition On/Start Switch Circuit Low Voltage code (P129D)?

- The code P129D can be triggered by issues such as a faulty fuel pump driver control module, a defective ignition switch, wiring problems, or a low voltage condition in the circuit.

3. How can I diagnose the cause of OBDII code P129D?

- Diagnosing the code P129D typically involves using a scan tool to read the code, checking the fuel pump driver control module, inspecting the wiring for damage, and testing the ignition switch for proper functionality.

4. Is it safe to drive with the P129D code illuminated?

- It is not recommended to drive with the P129D code illuminated, as it can lead to potential issues with starting the vehicle or fuel delivery, which may result in a breakdown.

5. Can I reset the P129D code and see if it comes back?

- While you can clear the code temporarily, it is advisable to diagnose and repair the underlying issue causing the code P129D to prevent further problems with the vehicle's fuel system.

6. How much does it typically cost to repair OBDII code P129D?

- The cost of repairing the P129D code can vary depending on the specific cause. It may range from a simple fix like replacing a faulty component to more involved repairs involving the fuel pump driver control module or wiring.

7. Are there any DIY repair tips for addressing code P129D?

- DIY repair tips for code P129D may include checking and cleaning electrical connections, inspecting for damaged wires, and ensuring proper grounding of components in the fuel pump driver control module circuit.

8. Will OBDII code P129D affect my vehicle's performance?

- Yes, the P129D code can impact your vehicle's performance by causing starting issues, engine stalling, rough idling, and potentially affecting fuel delivery, leading to decreased efficiency.

9. Can a mechanic easily diagnose and fix the P129D code?

- A qualified mechanic with experience in diagnosing and repairing electrical issues should be able to efficiently diagnose and fix the P129D code by following proper diagnostic procedures.

10. How urgent is it to address OBDII code P129D once it appears?

- It is recommended to address the P129D code promptly to prevent potential issues with starting the vehicle, engine performance, and fuel delivery, which can lead to further damage if left unresolved.

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