P0256
Injection Pump Fuel Metering Control B (Cam/Rotor/Injector)
Fuel injection (diesel)
Generic OBD-II
High
What it means
P0256 means the engine controller has found a fault in the "B" fuel-metering control of the diesel injection pump — the part that governs how much fuel the pump delivers. Because this directly controls fueling, the engine can run poorly, stall, or refuse to start. The usual culprits are the metering actuator, a restricted fuel supply, or its wiring.
High
Can I keep driving? Risky — this affects how much fuel the pump delivers, so the engine may run poorly, stall, or be hard to start. Fix it before relying on the vehicle.
Common symptoms
What you'll notice
- Check-engine light on
- Hard starting or a no-start
- Rough running, surging, or stalling
- Reduced power and poor acceleration
- Possible extra exhaust smoke
Common causes
Most likely first
- Faulty injection pump fuel metering control actuatorLikely
- Restricted fuel supply — clogged fuel filter or blocked lineCommon
- Low fuel pressure or air in the fuel systemCommon
- Damaged wiring or connector in the metering control circuitLess often
- Failed engine control module (least likely)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check fuel supply pressure at the pump.
- Replace a clogged fuel filter and confirm the supply system is free of restrictions or air leaks.
- Inspect the metering control actuator wiring and connector for damage or corrosion.
- Test the fuel metering actuator; if the pump's metering control is confirmed faulty, the pump/actuator may need replacement.
- Only after supply and wiring check out, have the ECM evaluated. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0256?+
Not really — fuel metering faults can cause stalling or a no-start, which can leave you stranded. Have it diagnosed before longer trips.
Can I just clear P0256?+
It will return, and possibly with worse running, until the pump metering, fuel supply, or wiring problem is repaired.
Related codes
Often seen with P0256
Read & clear P0256 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX