Injection Pump Fuel Metering Control A Intermittent (Cam/Rotor/Injector)
P0255 indicates the engine computer detected an intermittent problem with the injection pump fuel metering control circuit, typically related to the fuel rail pressure (FRP) sensor or its signal wiring. This code is most common in diesel engines and affects the precise timing and amount of fuel delivered to the injectors.
What You Might Notice
- Check Engine Light illumination
- Decreased fuel economy
- Rough idle or engine hesitation
- Reduced engine power or performance
- Intermittent starting difficulty
Most Common Causes
- 1
FRP Sensor Signal Circuit Issues
Open circuit, short to voltage, or short to ground in the fuel rail pressure sensor signal wiring or connector. This prevents accurate fuel metering feedback to the engine computer.
- 2
Faulty Fuel Rail Pressure Sensor
A failing or defective FRP sensor that produces intermittent or incorrect voltage signals, causing the computer to lose proper fuel metering control.
- 3
Corroded or Loose Electrical Connectors
Poor connections at the FRP sensor connector or related circuit connectors create intermittent signal loss during engine operation.
- 4
Injection Pump Metering Control Solenoid Failure
A malfunctioning fuel metering solenoid in the injection pump itself may not respond properly to electronic control signals.
How to Diagnose It
- 1
Check FRP Sensor Signal Circuit Issues — Open circuit, short to voltage, or short to ground in the fuel rail pressure sensor signal wiring or connector. This prevents accurate fuel metering feedback to the engine computer.
- 2
Check Faulty Fuel Rail Pressure Sensor — A failing or defective FRP sensor that produces intermittent or incorrect voltage signals, causing the computer to lose proper fuel metering control.
- 3
Check Corroded or Loose Electrical Connectors — Poor connections at the FRP sensor connector or related circuit connectors create intermittent signal loss during engine operation.
- 4
Check Injection Pump Metering Control Solenoid Failure — A malfunctioning fuel metering solenoid in the injection pump itself may not respond properly to electronic control signals.
How to Fix It
- 1
Inspect and Test FRP Sensor Circuit
Visually inspect the fuel rail pressure sensor connector and wiring for corrosion, damage, or loose connections. Use a multimeter to test signal voltage and continuity. Repair or replace damaged wiring as needed.
- 2
Replace Fuel Rail Pressure Sensor
If testing confirms the FRP sensor is providing intermittent or out-of-range signals, replace the sensor with a factory or OEM-equivalent unit and retest.
- 3
Clean Connectors and Repair Wiring
Disconnect and clean the FRP sensor connector with electrical contact cleaner. Check for corrosion on pins and repair or splice any damaged signal wiring. Apply dielectric grease to reconnected terminals.
- 4
Inspect Injection Pump Metering Control
If the sensor and wiring test good, have the injection pump metering solenoid or control valve inspected by a diesel specialist. It may require cleaning, repair, or replacement.
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