AutoCodes – GMC – P129B 2016 GMC Sierra

P129B 2016 GMC Sierra Code - Fuel Pump Driver Control Module System Voltage Low

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: P129B 2016 GMC Sierra indicates Fuel Pump Driver Control Module System Voltage Low.
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 145

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 P129B 2016 GMC Sierra 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 Power Control Module detects the battery positive voltage is less than 7 V for 1 s.

OBDII Code P129B 2016 GMC Sierra - Fuel Pump Driver Control Module System Voltage Low - AutoCodes.com — P129B 2016 GMC Sierra Code - Fuel Pump Driver Control Module System Voltage Low

What does this mean?

What are the Possible Causes of the DTC P129B 2016 GMC Sierra?

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 P129B 2016 GMC Sierra?

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 P129B 2016 GMC Sierra 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 P129B 2016 GMC Sierra code?

Need more information on how to fix the P129B 2016 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

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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 P129B 2016 GMC Sierra Code

1. What does the OBDII code P129B mean on a 2016 GMC Sierra?

P129B indicates that the Fuel Pump Driver Control Module (FPCM) has detected a system voltage that is lower than the specified range.

2. What are the common symptoms of the P129B code in a 2016 GMC Sierra?

Symptoms may include difficulty starting the engine, poor engine performance, stalling, or the check engine light turning on.

3. What causes the P129B code to appear on a 2016 GMC Sierra?

Possible causes include a weak or failing battery, faulty alternator, poor wiring connections to the FPCM, or a failing Fuel Pump Driver Control Module.

4. Can a bad fuel pump trigger the P129B code?

A failing fuel pump itself is unlikely to cause this code, but issues with the module that controls the fuel pump, such as the FPCM, could trigger it.

5. How do you diagnose the P129B code on a 2016 GMC Sierra?

Diagnosis involves checking the battery voltage, inspecting the wiring and connectors to the FPCM, testing the alternator output, and scanning for additional trouble codes.

6. Can I drive my 2016 GMC Sierra with the P129B code?

It is not recommended, as low voltage in the FPCM system can lead to poor engine performance, stalling, or even a no-start condition.

7. How is the P129B code typically repaired?

Repairs may include replacing a failing battery, repairing damaged wiring or connectors, replacing the alternator, or replacing the Fuel Pump Driver Control Module.

8. How much does it typically cost to fix the P129B code on a 2016 GMC Sierra?

Repairs can cost between $100 and $600 depending on whether the issue is related to the battery, wiring, alternator, or FPCM.

9. Can a software update fix the P129B code on a 2016 GMC Sierra?

In some cases, a software update to the FPCM may resolve the issue if it's caused by a programming error, but this is less common than hardware-related problems.

10. How can I prevent the P129B code from recurring in my 2016 GMC Sierra?

Regular maintenance, including checking battery health, ensuring secure wiring connections, and monitoring alternator performance, can help prevent voltage-related issues.