P0629 Fuel pump control circuit “A” high

P0951 – OBD-II Trouble Code Technical Description

Trouble code P0629 indicates that the voltage in the fuel pump control circuit is too high (compared to the value specified in the manufacturer's specifications).

What does trouble code P0629 mean?

Trouble code P0629 indicates that too high voltage has been detected on the fuel pump control circuit. This means that the engine control module (PCM) or other vehicle control modules have detected that the fuel pump control circuit voltage is higher than the specified voltage, which may indicate a problem with the fuel management system.

Possible reasons

Several possible reasons for the P0629 trouble code:

• Fuel pump malfunction: Problems with the fuel pump itself, such as wear, damage, or malfunction, can cause the control circuit voltage to be too high.
• Wiring and Connectors: Damaged or oxidized wires or faulty connectors in the fuel pump control circuit can cause an increase in voltage.
• Malfunction of the fuel level sensor or sensors: Problems with the fuel level sensor or other sensors included in the fuel management system can cause the fuel level to not be read correctly and therefore lead to the P0629 code.
• Problems with the PCM or other control modules: Malfunctions in the PCM or other vehicle ancillary control modules can cause the fuel pump control circuit to incorrectly process data and monitor voltage.
• Electrical problems: A short circuit, overload, or other electrical problem in the vehicle's control system may cause an increase in voltage in the fuel pump control circuit.

These possible causes should be considered during diagnosis to determine the correct source of the problem and correct it.

What are the symptoms of a fault code? P0629?

Symptoms for DTC P0629 may vary depending on the specific problem and vehicle characteristics:

• Using Backup Mode: The PCM can put the vehicle into a standby mode to prevent possible damage to the engine or control system.
• Uneven engine operation: Unstable engine operation or rough idling may be due to problems in the fuel pump control system.
• Loss of power: Increasing the voltage on the fuel pump control circuit may result in loss of engine power and poor acceleration.
• Difficulty starting the engine: Problems with the fuel pump control can make the engine difficult or even impossible to start.
• Increased fuel consumption: Improper operation of the fuel management system can result in increased fuel consumption due to inefficient combustion or the engine constantly running rich.
• Check Engine Light Appears: One of the main symptoms of the P0629 code will be the Check Engine light on your vehicle's dashboard coming on.

How to diagnose a fault code P0629?

The following steps are recommended to diagnose DTC P0629:

1. Checking Error Codes: Use a diagnostic scanner to read error codes in the engine management system. Check to see if there are other error codes that may further indicate problems with the system.
2. Visual inspection: Inspect the wires, connectors, and connections in the fuel pump control circuit for damage, wear, or oxidation. Make sure all connections are secure and connected correctly.
3. Voltage test: Using a multimeter, measure the voltage at the fuel pump control circuit. Make sure the voltage is within the range specified by the manufacturer.
4. Checking the fuel pump: Diagnose the fuel pump itself, including its operation and electrical circuit. Make sure the fuel pump is working properly and that its electrical circuit is intact.
5. Checking fuel level sensors: Check the condition and proper operation of the fuel level sensors, as they can also affect the operation of the fuel management system.
6. Diagnosis of PCM and other control modules: Check the condition of the PCM and other auxiliary control modules that may be related to fuel pump control. If necessary, program or replace the module.
7. Error code reset and testing: Once the problem is found and corrected, use the diagnostic scanner again to reset the error code. After this, road test the vehicle to ensure the problem is resolved.

If you do not have the experience or necessary equipment to perform diagnostics and repairs, it is recommended that you contact a qualified auto mechanic or auto repair shop for professional assistance.

Diagnostic errors

When diagnosing DTC P0629, the following errors may occur:

• Misinterpretation of data: Incorrect understanding of data from diagnostic tools or misinterpretation of test results may lead to incorrect diagnosis and resolution of the problem.
• Problems with wiring or connections: Faults or poor connections in wiring or connectors may result in incorrect test results and incorrect diagnosis.
• Insufficient diagnosis: Insufficient testing or omission of important fuel management system components may result in incomplete or inaccurate diagnosis.
• Incorrect component replacement: Replacing components without proper diagnosis and confirmation of their malfunction can lead to unnecessary costs and failure to solve the problem.
• Problems in other systems: Some symptoms associated with the P0629 code can be caused not only by a fault in the fuel pump control circuit, but also by problems in other vehicle systems, such as the electrical system or engine sensors.
• Malfunctions of the PCM or other modules: Ignoring possible faults in the PCM or other vehicle control modules that may be related to fuel pump control may result in incorrect diagnosis and repair.

To avoid these errors, it is important to follow strictly defined diagnostic procedures and use the correct diagnostic tools.

How serious is the fault code? P0629?

Trouble code P0629 can be serious because it indicates problems with the control of the fuel pump, which is an important component of the engine's fuel delivery system. If the problem remains unresolved, it can result in the engine not running properly, not receiving enough fuel, or even stopping completely, potentially causing the engine to fail and the vehicle to stop on the road.

Additionally, high voltage in the fuel pump control circuit can overload the vehicle's electrical system, which can lead to additional problems with the vehicle's electrical and electronics.

Therefore, it is recommended that you contact a qualified auto mechanic for diagnosis and repair as soon as possible to avoid serious consequences and ensure the safe and reliable operation of your vehicle.

What repair will help eliminate the code? P0629?

Resolving the P0629 trouble code depends on the specific cause that caused it to appear, some general steps that may help resolve this code are:

1. Checking and replacing the fuel pump: If the fuel pump is identified as the source of the problem, it must be diagnosed. If a malfunction is detected, the fuel pump should be replaced with a new or repaired one.
2. Checking and replacing wiring and connectors: Carry out a thorough check of the wiring, connectors and connections in the fuel pump control circuit. Replace damaged or oxidized wires and faulty connectors.
3. Diagnostics and replacement of fuel level sensors: Check the operation and condition of the fuel level sensors. If necessary, replace defective sensors.
4. Checking and replacing the PCM or other control modules: If other control system components are also identified as the source of the problem, diagnose them and, if necessary, replace or reprogram them.
5. Programming: In some cases, programming or software updates may be required in the PCM or other control modules to correct the problem.
6. Additional repair measures: Depending on your specific circumstances, additional repairs may be required, such as replacing fuses, relays, or other electrical system components.

It is important to note that to effectively resolve the P0629 code, it is recommended that you contact a qualified auto mechanic or auto repair shop, especially if you do not have the necessary experience and equipment to diagnose and repair.

What is P0629 Engine Code [Quick Guide]

P0629 – Brand-specific information

Trouble code P0629 is associated with high voltage in the fuel pump control circuit, decoding for some specific brands of cars:

• Ford: This error code may be related to fuel pump control problems. For example, in a Ford it may indicate problems with the high pressure fuel pump (HPFP).
• Chevrolet/GMC: On Chevrolet and GMC vehicles, this code may indicate problems with the fuel pump or its electrical circuit.
• Toyota: On Toyota vehicles, this error code may indicate a problem with the fuel delivery system, possibly related to the fuel pump.
• Honda: On Honda vehicles, the P0629 code may be associated with problems in the electrical control circuit of the fuel pump or the pump itself.
• Volkswagen/Audi: On Volkswagen and Audi vehicles, this code may indicate problems with the fuel pump electrical circuit or sensors.
• BMW: On BMW vehicles, this code may indicate problems with high pressure in the fuel system, possibly related to the high pressure fuel pump.
• Mercedes-Benz: On Mercedes-Benz vehicles, this error code may be related to problems with the fuel pump control circuit or its operation.
• Hyundai / Kia: On Hyundai and Kia vehicles, the P0629 code may indicate problems with the fuel pump electrical circuit or assembly.

This is general information only and specific diagnostic procedures may vary depending on the model and year of your vehicle. If this code occurs, it is recommended that you consult the repair manual for your specific vehicle make and model for more accurate diagnosis and repair.