The P0254 code indicates a malfunction in the fuel metering control circuit of injection pump “A”, with a signal that is too high detected. This typically concerns diesel engines and often involves an electrical issue in the fuel rail pressure (FRP) sensor circuit or the fuel metering actuator.
⚙️ Summary of Code P0254
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Full name: P0254 – Injection Pump “A” Fuel Metering Control, High Signal (cam/rotor/injector)
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Severity: Low to moderate — risk of inefficient engine operation, but rarely immobilizing
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Code type: OBD-II, especially on diesel engines
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Role of the affected part: To precisely regulate the amount of fuel injected according to engine demand
🔧 Possible Causes
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✅ Short circuit to voltage in the FRP sensor signal wire
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✅ Open wires or loose/corroded/melted connector
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✅ Defective FRP (Fuel Rail Pressure) sensor
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⛔ Defective PCM (engine control module) (rare)
⚠️ Typical Symptoms
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Illumination of the check engine light (MIL)
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Reduced engine performance
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Loss of fuel economy
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Rough idle or stalling
🛠️ Diagnostic/Repair Steps
1. Visual Inspection
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Locate the FRP sensor (often attached to the injection pump),
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Carefully inspect:
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Cut, melted, or corroded wires,
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Loose or oxidized connectors (green tint),
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Clean and apply dielectric grease if necessary.
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2. Voltage Tests
Using a digital voltmeter (DVOM):
a. Power Supply Test
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Ignition on, engine off,
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Measure the voltage between the FRP sensor’s power terminal and ground.
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Expect approximately 5 to 12 volts depending on the system. If not within range, faulty wiring or PCM.
b. Signal Test
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Measure between the signal wire and ground,
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You should have about 5 volts if the sensor is idle. A persistent high voltage (>4.8V) triggers P0254.
3. Sensor Replacement
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If the voltage is still incorrect and the wiring is good, replace the FRP sensor.
4. Code Clearing and Road Test
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Clear the code with an OBD-II scanner,
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Test the vehicle under normal conditions,
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If the code returns: consider replacing the PCM (as a last resort, with reprogramming).
📌 Important Note
Some brands like Mercedes, VW, Ford, or GM have specific variations for this code. It may be helpful to consult TSBs (technical service bulletins) or have a manufacturer’s manual to know the specifics (exact location, wire colors, voltage ranges, etc.).