Fuel and air

P0257 — Injection Pump Fuel Metering Control 'B' Range/Performance Fault

Severity: medium Drive with care, to a shop

What P0257 means

The engine control unit controls how much fuel a diesel injection pump delivers using a metering actuator and a rack or metering position sensor. P0257 sets when the actual position or response in circuit 'B' does not match the commanded value or falls outside the allowed range. The cause may be the sensor, actuator, wiring or the pump itself.

Symptoms

  • Check Engine light on
  • Rough or unstable idle
  • Hesitation and poor acceleration
  • Reduced power or limp mode
  • Higher fuel consumption
  • Unusual exhaust smoke
  • Hard starting or irregular running

Possible causes

  1. Faulty fuel rack position sensor or fuel metering actuator
  2. Damaged wiring or corroded connector in the pump control circuit
  3. Internal mechanical wear or failure of the injection pump
  4. Clogged fuel filter or restricted fuel supply
  5. Air in the fuel system or low lift pump pressure
  6. ECM fault (rare)

How to diagnose

  1. Scan all codes and freeze frame data, and note any related fuel or sensor codes
  2. Inspect the pump harness and connector for breaks, chafing, moisture and corrosion
  3. Check supply voltage, ground and sensor or actuator resistance against specifications
  4. Check the fuel filter and supply pressure, and rule out air leaks
  5. Compare commanded and actual metering position in live data
  6. Check injector operation and cylinder balance
  7. If the electrical side is good, have the pump tested by a diesel specialist

Common fixes

  • Repair wiring and connectors in the metering circuit
  • Replace the rack position sensor or metering actuator
  • Replace the fuel filter, fix air leaks and restore fuel supply
  • Rebuild or replace the injection pump
  • Reprogram or replace the ECM only after confirming it is faulty

Questions and answers

What does P0257 mean?

It is a diesel fault for fuel metering control circuit 'B' on the injection pump. The actual metering position does not match the command or is out of range. The sensor, actuator or wiring is more often at fault than the pump itself.

Can I drive with P0257?

Briefly and carefully to a shop if the engine runs smoothly. Power loss and limp mode are likely, and a badly failing pump can make the engine stall.

What should I check first for P0257?

Start with the fuel filter, fuel supply and the pump wiring and connector. These are the easiest and most common causes, so check them before suspecting the pump.

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.