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P2633 OBD-II Trouble Code: Fuel Pump B Control Circuit Low

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P2633 code definition

The P2633 trouble code detects a problem with the fuel pump B control circuit.

What the P2633 code means

The P2633 code is a generic OBD-II trouble code. This code notes an issue with the fuel pump B control circuit, with the “B” referencing an of the control circuit. When the powertrain control module (PCM), or any number of other control modules (such as the antilock brake control module, fuel injection control module, or instrument panel control module) notices a fault in the fuel pump B control circuit, the P2633 code will be triggered.

What causes the P2633 code?

There are a few common causes for the P2633 code, including:

  • Malfunctioning fuel pump
  • Faulty fuel pump relay
  • Malfunctioning controller area network (CAN) bus
  • Shorted or corroded wires, or open connectors in the CAN bus harness
  • Broken ground wire
  • Loose or broken control module ground strap
  • In rare cases, a faulty PCM or other control module

What are the symptoms of the P2633 code?

The P2633 trouble code will usually be accompanied by an illuminated Check Engine Light. The vehicle may also illuminate the fuel cap malfunction warning light. There are unlikely to be any drivability issues with the P2633 code.

How does a mechanic diagnose the P2633 code?

The P2633 code will be diagnosed using a normal OBD-II trouble code scanner. A certified mechanic will look at the freeze frame data for the P2633 code to assess the issue, and to look for any additional trouble codes that may be detected. Next, the technician will reset the trouble codes and restart the vehicle to see if the code persists. If the code does not return, it was likely triggered erroneously.

If the P2633 trouble code is still detected after the restart, the technician will have to begin inspection of the CAN bus and the fuel pump. The mechanic will start with the wires, connectors, and ground straps, because they offer the easiest and most cost-effective repair. If no issues are noted there, the technician will move to the CAN bus and the fuel pump. It is best for the technician to use a CAN scanner when inspecting the CAN bus.

When any component is replaced, the technician will reset the trouble codes and restart the vehicle again, before continuing with further inspection.

Common mistakes when diagnosing the P2633 code

The most common issue when diagnosing the P2633 code comes from a failure to follow the basic trouble code diagnosis protocol. All steps of the protocol should be followed in order to ensure that the mechanic not only finds and resolves the issue, but does so in the timeliest and most cost-effective manner possible.

Failure to follow the standard diagnosis protocol can result in replacing the fuel pumps or fuel pump relays when the issue was with the communication from the CAN bus.

How serious is the P2633 code?

The P2633 trouble code will not keep a vehicle from operating and being drivable. However, the code should still be addressed and the issue resolved as soon as the P2633 code is detected.

What repairs can fix the P2633 code?

Some of the most common fixes for the P2633 trouble code include:

Additional comments for consideration regarding the P2633 code

Failure to use a CAN scanner when inspecting the P2633 code may result in the need to disconnect and inspect each pin of the CAN bus manually, which is a very time intensive endeavor.

Need help with a P2633 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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