P0251 - INJECTION PUMP FUEL METERING CONTROL A MALFUNCTION

The injection pump control circuit “A” can be located inside, on the side, or built into the injection pump. This circuit is comprised of the Fuel Rail Pressure (FRP) Sensor and a fuel quantity actuator.

The FRP sensor converts the amount of diesel fuel delivered by the actuator into an electrical signal. This information is then sent to the Powertrain Control Module (PCM), which uses it to determine the amount of fuel to be placed in the engine according to the engine’s operating conditions.

If the input does not match the normal operating conditions of the engine, which are stored in the memory of the PCM, the fault code P0251 OBDII is set.

• Check Engine light on.
• Difficulties in starting the engine.
• The fuel economy decreases.
• Excessive smoke from the exhaust.

The reasons for setting the diagnostic code P0251 OBD2 are

• Fuel Rail Pressure (FRP) signal circuit may be short-circuited.
• Short to voltage or ground of FRP sensor.
• The FRP sensor may be defective.

To solve the problems related to the DTC code P0251 OBD II, you must do the following:

• The first thing you need to do is consult the Technical Service Bulletins (TSB). The solution may be known by the manufacturer.
• After locating the Fuel Rail Pressure Sensor (FRP), check the connector and all cables. If you find that any of these components are corroded, worn, repair, or replace them. Also, check the terminals inside the connector. Clear the code and see if it comes back.
• If the code returns, check the FRP sensor and its circuitry. To do this, unplug the connector on the Fuel Rail Pressure. Then, plug a black wire from a voltmeter to the ground terminal on the wiring harness connector and the red wire to the power terminal. Then, put the key in the ignition position with the engine off, there should be between 5 to 12 volts. Check the manufacturer's specifications. If they do not match, repair the power or ground wire.
• Check the signal cable having the connector unplugged, connect the red multimeter wire to the terminal of the signal cable. The result is that there should be 5 volts. If not, repair the signal wire.
• Change the FRP sensor.