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P0628 OBD-II Trouble Code: Fuel Pump “A” Control Circuit Low

Check Engine Light

P0628 code definition

If the PCM (powertrain control module) or one of its supporting control modules (e.g., antilock brake control module, fuel injection control module, cruise control module, etc.) detects a fault in the fuel pump “A” control circuit, it will store the P0628 code and illuminate the Check Engine light. In some vehicles, the code will be stored after a single faulty signal, while in others up to eight drive cycles may be required for the code to be stored.

What the P0628 code means

A P0628 code indicates that there is a problem in the fuel pump control circuit, due to a voltage reading that is outside the manufacturer’s approved settings for the vehicle.

What causes the P0628 code?

The P0628 code is most often stored due to one of the following causes:

  • A defective fuel pump
  • An open or shorted fuel pump wiring harness
  • A poor electrical connection to the fuel pump
  • A defective fuel pump relay

If your vehicle has a fuel pump control module, this could also be defective and cause the code to be stored.

What are the symptoms of the P0628 code?

In addition to the Check Engine light going on, your vehicle may also illuminate a Fuel Cap Malfunction light when the P0628 code is stored. In most cases, these are the only symptoms associated with the code.

How does a mechanic diagnose the P0628 code?

The first diagnostic step will always be to use an OBD-II scanner to check for all codes stored by the PCM at the moment. Once the P0628 code is identified, the mechanic will do a visual inspection of the wiring and connectors to ensure that the problem is not on the fuel pump control circuit. They’ll then clear the code and retest the system to see if the problem has been resolved. Moving forward, with each step, inspection, and repair, the mechanic will systematically clear the code(s) and retest the system again. Once the diagnostic process is complete, the mechanic should have found the problem and should be able to address it quickly.

Common mistakes when diagnosing the P0628 code

When a communications code like P0628 is stored, other codes are often stored with it. When this happens, it’s fairly common for an untrained person to address other codes and symptoms first. These codes will almost always be resolved when the root case of the P0628 code is addressed.

How serious is the P0628 code?

Some people assume that a P0628 code is not very serious because it is not usually accompanied by any noticeable symptoms other than the Check Engine light and the Fuel Cap Malfunction light being illuminated. However, this code can trigger other codes, and those codes may severely affect the performance of your vehicle. If left unresolved, this code could result in lasting damage to the vehicle.

What repairs can fix the P0628 code?

The most common repairs performed to fix a P0628 code include:

  • Repairing or replacing a defective or damaged fuel pump relay
  • Repairing or replacing loose or broken wiring or connectors
  • Replacing the fuel pump wiring harness
  • Replacing a defective fuel pump

Additional comments for consideration regarding the P0628 code

While it will likely have no noticeable symptoms affecting the drivability of the car, the P0628 code should be addressed as soon as possible. This code can cause a number of other problems, which can have significant drivability and performance symptoms. It can also keep the vehicle from passing an OBD-II emissions test, thereby making it impossible to legally register the vehicle until the problem is resolved.

Need help with a P0628 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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