AutoCodes – Cadillac – P0629 Cadillac

P0629 Cadillac 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 Cadillac 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 557

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

What does this mean?

What are the Possible Causes of the DTC P0629 Cadillac?

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 Cadillac?

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 Cadillac 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.

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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 P0629 Cadillac Code

1. What does the OBDII code P0629 mean on a Cadillac?

P0629 indicates a "Fuel Pump Speed Output Circuit High Voltage," meaning the engine control module (ECM) has detected an unusually high voltage in the fuel pump speed control circuit.

2. What are the common symptoms of a P0629 code on a Cadillac?

Symptoms may include engine stalling, difficulty starting the engine, poor fuel efficiency, and possibly an illuminated check engine light.

3. What causes the P0629 code on a Cadillac?

Common causes include a faulty fuel pump control module, damaged wiring or connectors in the fuel pump circuit, or a malfunctioning ECM.

4. Can I drive my Cadillac with a P0629 code?

Driving with a P0629 code is not recommended, as it can lead to engine stalling and unreliable fuel delivery, which may leave you stranded or damage other components.

5. How do I diagnose a P0629 code on a Cadillac?

Start by checking the fuel pump control module, inspecting the wiring and connectors for damage or corrosion, and testing the fuel pump circuit voltage with a multimeter.

6. How do I fix the P0629 code on a Cadillac?

Repairs may include replacing a faulty fuel pump control module, repairing or replacing damaged wiring, or reprogramming or replacing the ECM if necessary.

7. How much does it cost to fix a P0629 code on a Cadillac?

Repair costs vary but typically range from $150 to $500, depending on the specific issue, such as a faulty module or wiring repair.

8. Can a weak battery cause the P0629 code on a Cadillac?

Yes, a weak or failing battery can cause voltage irregularities that may trigger the P0629 code.

9. Will clearing the P0629 code fix the problem on my Cadillac?

Clearing the code will turn off the check engine light temporarily, but the underlying issue must be fixed to prevent the code from returning.

10. Does the P0629 code indicate a fuel pump failure on a Cadillac?

Not necessarily. While the fuel pump could be at fault, the issue is more often related to the control module, wiring, or voltage regulation in the circuit.