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Engine-Codes – GMC – P0629 Gmc

P0629 Gmc Code - Fuel Pump Speed Output Circuit High Voltage

Quick Answer

The P0629 Gmc code indicates a problem with the fuel pump speed output circuit having high voltage. Common causes include Malfunctioning fuel pump, Faulty fuel pump relay, Damaged wiring in the fuel pump speed output circuit. 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 Malfunctioning fuel pump, Faulty fuel pump relay, Damaged wiring in the fuel pump speed output circuit.
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 12, 2024
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Code P0629 Gmc Description

The P0629 Gmc code indicates a problem with the fuel pump speed output circuit having high voltage. This means that the engine control module (ECM) has detected that the voltage in the fuel pump speed output circuit is higher than the specified range. The fuel pump speed output circuit is responsible for controlling the speed of the fuel pump, which is essential for delivering the correct amount of fuel to the engine.

OBDII Code P0629 Gmc - Fuel Pump Speed Output Circuit High Voltage
P0629 Gmc Code - Fuel Pump Speed Output Circuit High Voltage

Common Causes of P0629 Gmc

  1. Malfunctioning fuel pump
  2. Faulty fuel pump relay
  3. Damaged wiring in the fuel pump speed output circuit
  4. Issue with the engine control module (ECM)
  5. Corrosion or loose connections in the circuit

Symptoms of P0629 Gmc

  1. Poor fuel efficiency
  2. Engine stalling
  3. Rough idling
  4. Engine not starting
  5. Check engine light illuminated

How to Fix P0629 Gmc

  1. Perform a diagnostic scan to confirm the P0629 code and identify the exact cause of the issue.
  2. Inspect the fuel pump, relay, and wiring harness for any visible damage or corrosion.
  3. Test the fuel pump speed output circuit using a multimeter to check for proper voltage levels.
  4. Replace any faulty components such as the fuel pump, relay, or damaged wiring.
  5. Clear the code from the ECM memory and perform a test drive to ensure the issue has been resolved.

Cost to Fix P0629 Gmc

The typical repair costs for addressing a P0629 Gmc code can vary depending on the specific cause of the issue. In general, replacing a fuel pump or relay can range from $200 to $600, while repairing wiring harnesses or the ECM can be more expensive, costing up to $1000 or more. Labor costs can add another $100 to $300 to the total repair bill. It's important to note that these are rough estimates, and actual costs may vary based on various factors. It is recommended to consult with a qualified mechanic or auto repair shop for a more accurate cost estimate.

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Information for Specific GMC Models

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.

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