Injection Pump Fuel Metering Control "B" Malfunction (Cam/Rotor/Injector)
The engine's fuel injection pump isn't precisely controlling how much fuel enters the cylinders, similar to a faucet that won't deliver water at the right pressure. The ECU detected that the pump's metering valve (rotor or cam) isn't responding correctly to commands.
The ECU monitors the fuel metering control solenoid voltage and current response in the injection pump's rotor mechanism. It measures command signal delivery versus actual pump response to detect mechanical wear, electrical faults, or blockages. When actual fuel delivery deviates from the commanded rate, the fault is logged.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Solenoid Response Time | 5-15 milliseconds activation delay | >25 ms or no response detected |
| Fuel Metering Pressure | Within 10% of target command | >15% variance or sustained low pressure |
Code P0257 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0257 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.