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P0251 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P0251 is an OBD-II Code that refers to Injection Pump Fuel Metering Control A Malfunction

Meaning

A P0251 code is a general diagnostic trouble code that occurs when the ECM/PCM detects a problem with the injection pump fuel metering control circuit “A”. The fuel quantity actuator and a Fuel Rail Pressure (FRP) Sensor make up this circuit. The fuel delivered by the actuator is translated into an electrical signal by the FRP sensor. This data is transmitted to the Powertrain Control Module (PCM), which uses it to calculate the amount of fuel to be delivered to the engine in light of the engine’s current operating conditions.

The PCM will set code P0251 if it detects a problem with the way the fuel metering control actuator or sensor is functioning.

Causes

Common causes for this code include:

  • Open or shorted Electronic Fuel Control Actuator harness
  • Poor electrical connection in Electronic Fuel Control Actuator Circuit 
  • Contaminated, incorrect or bad gasoline
  • Dirty optical sensor
  • Clogged fuel pump, fuel filter or fuel injector
  • Bad intake air temperature sensor
  • Bad crankshaft position sensor
  • Bad accelerator pedal position sensor
  • Bad fuel control actuator
  • Bad PCM/ECM (rare)

Symptoms

The symptoms of a P0251 code are:

  • Illuminated Check Engine Light
  • Stalling and misfiring of the engine
  • Excessive smoke from the exhaust
  • Acceleration loss
  • Hard start or no start problems

Diagnosis

To diagnose a P0251 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect the engine control actuator harness and connector.
  3. Check the ECM power supply and ground circuits.
  4. Inspect the condition of the fuel and ensure it meets specifications.
  5. Clear all codes and road test to see if they come back on.
  6. If they do, check for resistance or shorts in the circuit with a multimeter between the PCM and the actuator.
  7. Check for proper operation of the fuel control actuator using a scan tool and command signals from the PCM.
  8. If all else fails, replace the Electronic Fuel Control Actuator or PCM.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P0251 code:

  • Not thoroughly inspecting all the wiring and connectors for damage.
  • Not checking for fuel starvation issues.
  • Not clearing the codes and testing to see if they return.
  • Failing to check for proper operation of the Electronic Fuel Control Actuator with a scan tool before replacing it.
  • Replacing the PCM without first checking all other possible causes.

How serious is this?

A P0251 code is a moderately serious diagnostic trouble code that can have a few different consequences if left unfixed. The most common is engine stalling and misfiring, which can lead to acceleration loss and even a hard start or no start problem. In some cases, excessive smoke may also come from the exhaust due to incomplete combustion.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Broken or faulty wirings must be repaired or replaced
  • Bad or contaminated gasoline must be replaced
  • Faulty sensors need to be repaired or replaced
  • Dirty optical sensors should be cleaned
  • Clogged fuel pump, filter, and injector must be replaced
  • Replace intake air temperature sensor
  • Replace crankshaft position sensor
  • Replace accelerator pedal position sensor
  • Replace fuel control actuator
  • Bad PCM/ECM may need to be replaced

Related codes

A P0251 is related to and may be accompanied by the following codes:

P0252 – Fuel Rail Pressure Sensing Circuit Low Voltage

P0253 – Fuel Rail Pressure Sensing Circuit High Voltage

P0254 – Fuel Rail Pressure Sensing Circuit Intermittent High Voltage

P0255 – Fuel Rail Pressure Sensing Circuit Intermittent Low Voltage

U1016 – Lost Communication With Fuel Metering Control Module

Conclusion

In conclusion, the P0251 code is a diagnostic trouble code that refers to a problem with the fuel metering control actuator or sensor. The most common symptoms are engine stalling and misfiring, as well as acceleration loss and hard starting or no starting. In some cases, excessive smoke may also come from the exhaust. The most common cause is a broken or faulty wiring, but other causes include contaminated gasoline, bad sensors, and clogged fuel injectors.

If you have a P0251 code, it’s important to get it checked out by a qualified technician as soon as possible to avoid further damage to your engine.