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P0256 OBD-II Trouble Code: Injection Pump Fuel Metering Control "B" Malfunction (Cam/Rotor/Injector)

check engine light

P0256 code definition

The P0256 Trouble Code indicates injection pump fuel metering control “B” malfunction (cam/rotor/injector).

What the P0256 code means

When this code appears, it means that the powertrain control module has found that the signal voltage to the electronic fuel control actuator and the signal returning from the fuel metering control sensor are incorrect. This code is only for diesel-powered vehicles, and it should never appear in non-diesel vehicles. If it does, it will mean there is an issue with the powertrain control module.

What causes the P0256 code?

Several different things could cause the P0256 code to appear, including the following:

  • Dirty fuel filter
  • Clogged fuel filter
  • Defective fuel pump
  • Shorted or open circuits
  • Shorted or open electrical connectors
  • Faulty fuel control actuator driver in the powertrain control module

What are the symptoms of the P0256 code?

The symptoms of the P0256 code can vary substantially. In some instances, the driver might only have the code stored in the vehicle and have to contend with a service engine soon light. However, it could be more problematic in other cases. Sometimes, there will be an excessive amount of smoke coming from the exhaust. There could also be engine misfires and hesitation when you are trying to accelerate. Other times, the vehicle might be difficult to start, or it might not start at all.

How does a mechanic diagnose the P0256 code?

The mechanic needs to connect to the vehicle’s onboard computer. Most vehicles over the last few decades have these computers inside them. The mechanic can hook up their OBD-II scanner to the computer to gather data about the codes and to help diagnose the issues with the vehicle. They will then reset the code and test the vehicle. They want to see if the code returns. If the code comes back, it means that it was not triggered by mistake, and then they can continue to look for the root cause of the problem.

Common mistakes when diagnosing the P0256 code

The most common mistake when diagnosing the P0256 code and trying to repair the vehicle is believing that the injector pump or the injectors are the problem. Most of the time, these will not need to be replaced. Instead, it is usually a problem with the fuel filter, or issues with the wiring.

How serious is the P0256 code?

While you might not always have many symptoms when you have the P0256 code, that doesn’t mean that you should drive your vehicle around in that condition. It still needs to be taken to a mechanic who can go over the vehicle and make all of the needed repairs. In addition, there is also the chance that the vehicle could start to run rough, or that it might not start at all.

What repairs can fix the P0256 code?

The following are some of the repairs and fixes that the mechanic could make to fix the P0256 code:

  • Check the vehicle using the OBD-II device
  • Reset the code and test the vehicle to see if it comes back
  • Check the electrical connections for corrosion and other issues
  • Replace the fuel filter
  • Replace the fuel pump
  • Replace the fuel control actuator driver in the powertrain control module

Additional comments for consideration regarding the P0256 code

Do not neglect your vehicle. Many drivers will have codes show up in their vehicle, but they opt not to do anything about them because they haven’t noticed a problem with the way their vehicle runs. This could be a mistake. The P0256 code might not have any effects other than an illuminated Check Engine Light. However, you don’t want to run the risk that one day you will head outside and find that your vehicle no longer starts or that you now have other codes and issues to contend with.

Need help with a P0256 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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