Fuel and air

P0255 — Injection Pump Fuel Metering Control "A" Intermittent

Severity: medium Drive with care, to a shop

What P0255 means

P0255 means the engine control module on a diesel intermittently sees a problem in the circuit that controls the fuel metering solenoid or actuator on the injection pump. The module normally commands fuel quantity with a controlled signal and checks the circuit or position feedback. When that signal drops out or is distorted, fuel delivery becomes unstable. Because the fault comes and goes, it may not show up all the time.

Symptoms

  • Check Engine light on
  • Intermittent loss of power
  • Rough idle
  • Hard starting or long cranking
  • Hesitation or stumbling on acceleration
  • Stalling, especially under load
  • Increased exhaust smoke

Possible causes

  1. Faulty fuel metering solenoid or actuator on the injection pump
  2. Damaged, corroded or loose connector or wiring in the metering circuit
  3. Intermittent open or short to ground in the harness caused by vibration
  4. Clogged fuel filter or restricted fuel supply
  5. Internal wear or damage in the injection pump
  6. Rarely, a faulty ECM

How to diagnose

  1. Read all codes and freeze frame data to see when the fault occurred
  2. Inspect the metering valve connector and harness for corrosion, chafing and loose terminals
  3. Wiggle the harness and connector with the engine running and watch for rpm changes or the code returning
  4. Test solenoid coil resistance and the power and ground supply per the factory wiring diagram
  5. Check low-pressure fuel supply, filter condition and air leaks in the fuel lines
  6. Compare commanded and actual rail pressure or actuator position in live data
  7. Scope the control signal to check its waveform
  8. Suspect the pump or ECM only after ruling out wiring and supply problems

Common fixes

  • Repair wiring and connectors and clean the terminals
  • Replace the fuel metering solenoid or actuator
  • Replace the fuel filter, fix air leaks and flush the lines
  • Repair or replace the injection pump
  • Replace or reprogram the ECM if confirmed faulty

Questions and answers

What does P0255 mean?

It is an intermittent fault in the injection pump fuel metering control circuit on a diesel. The ECM sees an incorrect signal from the solenoid or actuator and cannot always hold fuel delivery accurate.

Can I drive with a P0255 code?

Only briefly and carefully, to a repair shop. The engine may suddenly lose power or stall, so do not put off diagnosis.

Why does the code come and go?

Most often a poor connector contact or a damaged wire that behaves differently with vibration and heat. Start by inspecting the wiring.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.