AutoCodes – GMC – P129C GMC

P129C GMC Code - Fuel Pump Driver Control Module System Voltage High

Quick Answer

The Fuel Pump Power Control Module monitors the battery positive voltage circuit to verify the voltage is within the normal operating range. Common causes include Faulty Fuel Pump Driver Control Module, Fuel Pump Driver Control Module harness is open or shorted, Fuel Pump Driver Control Module 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: P129C GMC indicates Fuel Pump Driver Control Module System Voltage High.
Common causes: Common causes include Faulty Fuel Pump Driver Control Module, Fuel Pump Driver Control Module harness is open or shorted, Fuel Pump Driver Control Module 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 1,032

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 Jul 04, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P129C GMC Description

The Fuel Pump Power Control Module monitors the battery positive voltage circuit to verify the voltage is within the normal operating range. The Diagnostic Trouble Code (DTC) will be set when the Fuel Pump Driver Control Module detects the battery positive voltage is greater than 18 V for 1 s.

OBDII Code P129C GMC - Fuel Pump Driver Control Module System Voltage High - AutoCodes.com — P129C GMC Code - Fuel Pump Driver Control Module System Voltage High

What does this mean?

What are the Possible Causes of the DTC P129C GMC?

Faulty Fuel Pump Driver Control Module
Fuel Pump Driver Control Module harness is open or shorted
Fuel Pump Driver Control Module circuit poor electrical connection

How to Fix the DTC P129C 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 P129C 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 P129C GMC code?

Need more information on how to fix the P129C GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P129C GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

P129C 2014 GMC Sierra — Fuel Pump Driver Control Module System Voltage High
P129C 2015 GMC Sierra — Fuel Pump Driver Control Module System Voltage High
P129C 2016 GMC Sierra — Fuel Pump Driver Control Module System Voltage High
P129C 2017 GMC Sierra — Fuel Pump Driver Control Module System Voltage High
P129C 2018 GMC Sierra — Fuel Pump Driver Control Module System Voltage High

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 P129C GMC Code

1. What does the OBDII code P129C mean on a GMC vehicle?

P129C indicates that the Fuel Pump Driver Control Module (FPCM) has detected a system voltage that is higher than the expected range.

2. What are the common symptoms of the P129C code on a GMC?

Symptoms may include difficulty starting the engine, reduced fuel efficiency, poor engine performance, stalling, or an illuminated check engine light.

3. What causes the P129C code in a GMC vehicle?

Common causes include a faulty Fuel Pump Driver Control Module, damaged wiring or connectors, a failing fuel pump, or issues with the vehicle's electrical system, such as a faulty alternator or battery.

4. Is it safe to drive with a P129C code on a GMC?

Driving with a P129C code may cause performance issues and can lead to engine stalling. It's best to address the issue promptly to avoid further damage.

5. How do you diagnose the P129C code on a GMC?

Diagnosis involves using a scan tool to confirm the code, inspecting the wiring and connectors for damage, testing the Fuel Pump Driver Control Module, and checking the fuel pump and charging system for proper operation.

6. How can a P129C code be repaired on a GMC?

Repairs may include replacing the Fuel Pump Driver Control Module, repairing or replacing damaged wiring, fixing electrical system issues, or replacing the fuel pump if necessary.

7. Can a weak battery cause the P129C code on a GMC?

Yes, a weak or failing battery can lead to voltage irregularities, potentially triggering the P129C code.

8. How much does it typically cost to fix a P129C code on a GMC?

Repair costs vary depending on the root cause but can range from $100 for simple wiring repairs to $800 or more if the Fuel Pump Driver Control Module needs replacement.

9. Can a faulty alternator trigger the P129C code on a GMC?

Yes, a faulty alternator that provides inconsistent or high voltage to the system can cause this code to appear.

10. What tools are needed to repair the P129C code on a GMC?

Common tools include an OBDII scanner, a multimeter for electrical testing, and basic hand tools for inspecting and repairing wiring or replacing components.