P0251: Injection Pump Fuel Metering Control "A" (Cam/Rotor/Injector)

What P0251 means

P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 2, places it in the fuel and air metering, injector circuits subsystem; the last two digits identify the specific fault.

On diesel engines with an electronically controlled injection pump, a metering actuator (on the cam, rotor or injector, depending on design) sets how much fuel is delivered. The engine computer monitors its control circuit and position feedback.

The letter "A" distinguishes between two or more of the same component on one vehicle. Which physical part is "A" is set by the manufacturer, so confirm it in the service information before replacing anything.

What “Circuit” means here

"Circuit" is the broadest fault type in the standard. The module has found the diesel injection pump fuel metering control circuit electrically unusable: the signal is missing, outside its electrical limits, or the module's own self-test of the circuit failed. Some vehicles set this instead of the more specific low/high codes; others set it alongside them. Either way the first suspect is the wiring and connector, then the component, and only then the module.

What you may notice

Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0251:

• Hard starting
• Loss of power or limp-home mode
• Stalling
• Excess smoke

Where to start diagnosing P0251

1. Inspect pump connectors and harness for chafing and fuel contamination.
2. Check fuel quality and filter condition; restricted supply can make the metering control appear faulty.
3. Follow the manufacturer's procedure for pump actuator tests.

Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.

Live data to watch

These standard OBD2 values relate to P0251. Support varies by vehicle; a value your car does not report will simply be missing.

Related codes

Codes from the same diesel injection pump fuel metering control family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.

Further reading

• It cranks, but it will not fire
• It stalls when you come to a stop

Frequently Asked Questions