P0257
Injection Pump Fuel Metering Control B Range/Performance
If your code reader dashboard displays the generic DTC error code P0257, your vehicle is currently experiencing an active failure related to "Injection Pump Fuel Metering Control B Range/Performance". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
Code P0257 means your vehicle detected a problem with the injection pump fuel metering control b range/performance system. Drivers typically experience diesel engine knocking, loss of power when this code is active. This is a serious fault — avoid extended driving and have your vehicle inspected by a mechanic as soon as possible to prevent further damage.
Symptoms
Diesel engine knocking, loss of power
Common Causes
- Clogged fuel injectors
- Failed fuel metering control valve
- Incorrect engine timing
- Bad injection pump
How to Fix
- 1 Clean or replace injectors
- 2 Replace metering valve
- 3 Verify and adjust timing
- 4 Replace injection pump
Technical Explanation
Detection of P0257 occurs when the ECM cross-references multiple sensor inputs and determines that the reported values are physically inconsistent or out-of-range. Misfire rate is counted per cylinder over rolling windows and compared against two thresholds: a catalyst-damaging rate (triggers flashing MIL) and an emissions-exceeding rate (triggers solid MIL). The PCM logs which cylinder is misfiring based on crankshaft position at the time of each detected event. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
Driving with an active P0257 fault risks accelerating damage to clogged fuel injectors and related components. The longer the fault persists, the more expensive the eventual repair becomes — what starts as a sensor or solenoid issue can escalate to major mechanical failure.
Mechanic's Pro Tip
When diagnosing P0257, always test fuel volume delivery in addition to static pressure — a pump that holds pressure at idle but delivers insufficient volume under load will cause the fault only during acceleration or high demand, making it difficult to replicate in the driveway. Use a fuel pressure gauge with a volume outlet port: a healthy pump should deliver at least 1 liter per minute. Replace the fuel filter first; it's the cheapest test and solves the fault in a significant percentage of cases.
Injectors: 500 - 1,500; Pump: 1,000+