P0256 Code: Injection Pump Fuel Metering Control B Malfunction
🟠 Moderate severity · drivable
Drivable short-term, but the engine may run rough, lose power, or stall. Avoid long trips.
What P0256 means
The engine computer monitors a second fuel metering control (circuit B) inside the diesel injection pump. This code means that control circuit has a problem, so the pump may not be delivering fuel evenly or in the right amounts.
Symptoms
- Check engine light is on
- Hard starting or long cranking
- Rough idle or stalling
- Loss of power while driving
- Excessive smoke from the exhaust
Common causes
- most common: Faulty fuel metering component (circuit B) inside the injection pump
- common: Damaged wiring or a loose connector at the injection pump
- common: Worn or failing injection pump
- less common: Contaminated or watered-down diesel fuel
- rare: Engine computer fault
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Inspect and clean the injection pump connector | Yes | $0–20 |
| Repair damaged wiring to the injection pump | Mechanic | $50–200 |
| Replace or rebuild the injection pump | Mechanic | $1500–4000 |
Frequently asked questions
Can I drive with a P0256 code?
Yes for short trips, but the engine may run rough, lose power, or stall. If it won't restart, have it towed.
What is the most common cause of P0256?
A faulty fuel metering component inside the injection pump, or wiring and connector trouble at the pump.
What does circuit B mean in P0256?
The injection pump has more than one metering control circuit. Circuit A faults show as P0252–P0255, and circuit B faults show as P0256–P0260.
Related codes
P0257
P0257 Code: Injection Pump Fuel Metering Control B Out of Range
P0258P0258 Code: Injection Pump Fuel Metering Control B Signal Low
P0216P0216 Code: Injection Timing Control Circuit Malfunction
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.