AutoCodes – GMC – P0629 Gmc

P0629 Gmc Code - Fuel Pump Speed Output Circuit High Voltage

Quick Answer

The Engine Control Module (ECM) supplies voltage to the fuel pump driver control module for 30 s when the ignition is on and continuously when the engine is running. 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: P0629 Gmc indicates Fuel Pump Speed Output Circuit High Voltage.
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 487

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 15, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0629 Gmc Description

The Engine Control Module (ECM) supplies voltage to the fuel pump driver control module for 30 s when the ignition is on and continuously when the engine is running. While this voltage is being received, a serial data signal containing the desired fuel pump speed is also received from the ECM. After the voltage and data have been received the fuel pump driver control module actuates the brushless fuel pump by means of a high power three phase signal. The Diagnostic Trouble Code (DTC) will be set when the Fuel Pump Speed Output Circuit is short to voltage for greater than 2 s.

OBDII Code P0629 Gmc - Fuel Pump Speed Output Circuit High Voltage - AutoCodes.com — P0629 Gmc Code - Fuel Pump Speed Output Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0629 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
Faulty Engine Control Module (ECM)

How to Fix the DTC P0629 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 P0629 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 P0629 Gmc code?

Need more information on how to fix the P0629 Gmc code? Get Access to Factory Service Manuals

Need Help with the Code?

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Information for Specific GMC Models

P0629 2014 GMC Sierra — Fuel Pump Speed Output Circuit High Voltage
P0629 2015 GMC Sierra — Fuel Pump Speed Output Circuit High Voltage
P0629 2016 GMC Sierra — Fuel Pump Speed Output Circuit High Voltage
P0629 2017 GMC Sierra — Fuel Pump Speed Output Circuit High Voltage
P0629 2018 GMC Sierra — Fuel Pump Speed Output Circuit High Voltage

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 P0629 Gmc Code

1. What does the OBDII code P0629 mean for a GMC vehicle?

P0629 indicates a high voltage issue in the fuel pump speed output circuit, which can affect the proper operation of the fuel pump.

2. What are common symptoms of the P0629 code in a GMC?

Symptoms may include engine stalling, difficulty starting, poor fuel economy, or a check engine light.

3. What causes the P0629 code to appear?

Common causes include a faulty fuel pump relay, damaged wiring or connectors in the fuel pump circuit, or a malfunctioning powertrain control module (PCM).

4. Can I drive my GMC with the P0629 code?

Driving with this code is not recommended, as it may lead to fuel delivery issues that could cause engine stalling or failure to start.

5. How do I diagnose the P0629 code on my GMC?

Diagnosis involves checking the fuel pump relay, inspecting wiring and connectors for damage, and testing the fuel pump circuit with a multimeter.

6. What repairs are needed to fix the P0629 code?

Repairs may include replacing a faulty fuel pump relay, repairing or replacing damaged wiring or connectors, or reprogramming or replacing the PCM if necessary.

7. Could a failing fuel pump cause the P0629 code?

While a failing fuel pump itself is not a direct cause, issues in the related electrical circuit, such as high voltage, can trigger the code.

8. Does the P0629 code require reprogramming the PCM?

Reprogramming the PCM is only necessary if it is determined to be faulty or if an update is required as part of the repair.

9. How much does it cost to fix the P0629 code on a GMC?

Repair costs vary depending on the exact issue but typically range from $100 to $500, depending on whether it's a simple wiring repair or a component replacement.

10. Can a blown fuse cause the P0629 code?

A blown fuse in the fuel pump circuit can contribute to electrical irregularities, but this code specifically points to high voltage, so a fuse alone is unlikely to be the primary cause.