P0254 - Injection Pump Fuel Metering Control B High (Cam/Rotor/Injector)
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0254 is stored when the Engine Control Unit (ECU) detects a voltage signal from the fuel metering control circuit 'B' that is higher than the expected range. This typically refers to the solenoid or actuator on the high-pressure injection pump. The 'High' condition usually signifies a short circuit to voltage or an open circuit in the return line. Since the ECU manages fuel delivery via Pulse Width Modulation (PWM), a constant high signal prevents the system from regulating fuel volume and pressure. This disrupts the air-fuel ratio and can trigger an immediate Limp Home Mode or engine shutdown to prevent over-pressurization of the fuel rail.
Possible Causes
Short circuit to voltage in the wiring harness for the fuel metering valve.
Failing fuel metering solenoid (actuator) with an internal electrical fault.
Corroded or loose connector pins at the high-pressure pump.
Internal Engine Control Unit (ECU) failure in the driver circuit.
Symptoms
Recommended Solution
- Visual Inspection: Check the wiring and connector to the fuel metering solenoid on the high-pressure pump for chaffing, heat damage, or corrosion.
- Resistance Test: Disconnect the solenoid and measure internal resistance. Normal spec is typically between 1-5 Ohms. A reading of 0 Ohms indicates an internal short.
- Voltage Check: With ignition on, verify supply voltage at the connector. Check the signal wire for a short to 12V which would cause a constant 'High' state.
- Oscilloscope Analysis: Probing the PWM control signal during cranking or idling. A constant flat-line high signal confirms an electrical fault rather than a mechanical pump issue.
- Replacement: If wiring is intact, replace the fuel metering solenoid. If integrated, the high-pressure pump may need replacement. Clear codes and perform fuel system adaptation with a scan tool.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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