Fault code P0251 – injection pump fuel metering control “A” malfunction (cam/rotor/injector)

Fault code P0251 is called “Injection Pump Fuel Metering Control “A” Malfunction (Cam/Rotor/Injector)” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0251

OBD-II fault code P0251 is a generic fault code that is defined as a fuel metering pump control “A” fault. It is set when the Powertrain Control Module (PCM) detects a fault in the feedback signal circuits.

Fault code P0251 – injection pump fuel metering control

Incorrect characteristics are detected between the fuel metering control sensor, fuel quantity actuator. Also other sensors that are involved in determining fuel pressure and volume.

All Common Rail Diesel Injection systems use an “electronic fuel metering control actuator”. To measure the amount of fuel that is allowed into the pump chamber of a high pressure diesel fuel pump.

This determines the volume and pressure of the fuel that eventually enters the fuel rail. However, the pressure in the fuel rail must be monitored within a very narrow range.

For this purpose, in most cases a variable resistance pressure sensor is used to transmit the actual pressure to the PCM. This is done to ensure that the actual fuel rail pressure matches the calculated fuel rail pressure.

In a fully functional fuel system, the pressure sensor converts the fuel pressure into a voltage signal. This is used by the PCM to calculate injector pulse width and injection timing. To ensure that the right amount of fuel is injected into the cylinders under all operating conditions.

Thus, the signal voltages of the electronic fuel actuator and the fuel metering control sensor must match. In order for the PCM to calculate the appropriate fuel delivery strategy to ensure efficient engine operation at all rpm and loads.

Fault code P0251 associated with the fuel metering pump “A” may be set due to mechanical or electrical problems. Mechanical may include an EVAP problem, and electrical may include a faulty FRP sensor circuit.

Symptoms of vehicle malfunctions

The main signal that an error P0251 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
  2. Other related fault codes may also be present.
  3. Loss of power may be observed.
  4. The engine may become erratic.
  5. Increased fuel consumption.

The severity of fault code P0251 depends on the causes of its occurrence and may vary from medium to severe. But in any case, the error cannot be ignored, it is recommended to fix it as soon as possible.

Factors that can cause this error code

The error code P0251 can mean that one or more of the following problems have occurred:

  • Fuel rail position sensor (FRP) is defective.
  • Faulty fuel quantity actuator (FQA).
  • Damaged, burned, shorted, disconnected, corroded wires, or connectors.
  • Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P0251

Some suggested steps for troubleshooting and fix the error code P0251:

  1. Read all stored data and error codes with an OBD-II scan tool.
  2. Clear the error codes from the computer memory and test-drive the vehicle to find out if error P0251 appears again.
  3. Check the operation of the fuel rail position sensor (FRP).
  4. Test the fuel quantity actuator (FQA).
  5. Inspect the connectors and wiring for damage, looseness, and corrosion.

Diagnose and repair of problems

Before you start diagnosing the P0251 code, check the technical service bulletins (TSB) for your vehicle. The problem may be a known problem with a known fix issued by the manufacturer, which can save time and money.

Next, locate the fuel rail position sensor (FRP) on your car. It is usually located near the injection pump, bolted to the engine.

Visually inspect the connector and wiring, looking for scratches, scuffs, exposed wires, burnt areas, or melted plastic. Disassemble the connector and carefully inspect the terminals inside the connector.

If you need to clean the terminals, use an electrical contact cleaner and a brush with plastic bristles. Allow them to dry and apply electrical grease to the contact areas.

Using an OBD-2 scanner, clear the diagnostic trouble codes from the memory and see if the trouble comes back. If it does not, the problem was most likely in the connections.

Check the sensor and wiring

If the P0251 code returns, you should check the FRP sensor and related circuits. With the ignition off, disconnect the electrical connector on the FRP sensor.

Connect the black wire of the digital voltmeter to the ground terminal on the sensor wiring harness connector. Connect the red wire of the digital voltmeter to the power terminal on the sensor wiring harness connector.

Turn the key in the ignition, without starting the engine, the voltmeter should read 12 or 5 volts. If it does not, the problem may be with the power or ground wires, or related to a faulty PCM.

To check the PCM, you must test the signal wire. With the connector disconnected, move the red voltmeter wire from the power wire terminal to the signal wire terminal. The voltmeter should read 5 volts; if it does not, repair the signal wire or replace the PCM.

If all the checks are passed but you keep getting error P0251, the problem is most likely with a faulty FRP sensor. You can check the sensor with an ohmmeter and replace it with a new one if it is faulty.

On which vehicles does this problem occur most frequently

Fault code P0251 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • BAW
  • BMW
  • Chevrolet (Silverado, Trucks)
  • Dodge (RAM)
  • Ford (Connect, Fiesta, Mondeo, Transit)
  • GMC
  • Hyundai
  • Iveco (Daily)
  • Jaguar (X-Type)
  • Land Rover (Freelander, Range Rover)
  • LDV (Maxus)
  • Mercedes-Benz (Sprinter)
  • Mitsubishi (Fuso)
  • Opel (Astra)
  • Peugeot (Boxer)
  • Volkswagen
  • Volvo

Fault code P0251 can sometimes be found with other errors. The most common are the following: P0190, P0193, P0237, P0238, P0272, P0341, P0370, P0380, P0404, P0490, P0651, P0652, P1102, P1211, P1216, P2266, P2269, P2338, P2509, C1123, C1312.


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