P0255

Injection Pump Fuel Metering Control A Intermittent (Cam/Rotor/Injector)

P0255 is a generic OBD-II powertrain diagnostic trouble code: Injection Pump Fuel Metering Control A Intermittent (Cam/Rotor/Injector). It is logged by the engine control unit when the fuel/inj monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0255
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on)
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What P0255 means

P0255 is set when the engine control module (ECM) detects an intermittent, erratic signal from the fuel metering control circuit labelled "A" inside a distributor-type diesel injection pump. On platforms such as the Bosch VP44 (Dodge Cummins 5.9L 24v), Stanadyne DS4 (GM 6.5L), and Bosch VP on early Sprinter OM611, the ECM continuously monitors the pulse-width-modulated command sent to the metering solenoid and compares it against feedback from the cam/rotor position or fuel rack position sensor. An intermittent fault means the signal drops out, spikes, or disappears momentarily rather than remaining stuck, distinguishing this code from P0252 (low) or P0254 (high).

Because the condition is not continuous, the ECM may log the fault and restore normal operation within seconds, making real-world diagnosis challenging. The MIL illuminates and freeze-frame data is captured at the moment the out-of-range event occurs. Root causes span from corroded or loose electrical connectors in the metering solenoid harness, to a worn cam lobe or cracked distributor rotor producing irregular position pulses, to internal ECM driver-circuit degradation. Fuel contamination or restriction can also cause the solenoid to draw abnormal current, triggering intermittent detection.

Left unaddressed, repeated intermittent events can progress to a permanent fault, resulting in rough running, loss of power, and potential pump damage if the solenoid cycles erratically under load. Prompt inspection of the wiring harness and solenoid resistance is recommended before condemning the injection pump or ECM.

Common causes

Most-frequently reported root causes when P0255 is logged.

  • 1
    Corroded, loose, or damaged connector pins in the metering solenoid "A" wiring harness.
  • 2
    Worn cam lobe or cracked distributor rotor inside the injection pump producing irregular position pulses.
  • 3
    Defective or intermittently open fuel metering solenoid coil (check resistance against OEM spec, typically 10–30 Ω).
  • 4
    Chafed or broken wire creating a momentary open or short to ground in the solenoid control circuit.
  • 5
    Fuel contamination or severely clogged fuel filter causing abnormal solenoid current draw.
  • 6
    ECM internal driver-circuit degradation causing it to misread or drop the metering signal.
  • 7
    Moisture ingress into the pump-mounted position sensor or ECM connector.

Symptoms drivers notice

MIL (Check Engine Light) illuminated, often with intermittent blink during the fault event.
Momentary engine hesitation, stumble, or brief stall that self-clears within seconds.
Rough or surging idle with occasional RPM fluctuation.
Loss of power or jerky acceleration, particularly under load or when climbing grades.
Increased black or white exhaust smoke during the intermittent fault episode.
Hard starting or extended cranking on cold starts when the fault occurs at key-on.

How to diagnose P0255

A typical diagnostic flow when this code is present.

  1. 1
    Connect a professional OBD-II scan tool, retrieve freeze-frame data, and note engine load, RPM, and coolant temperature at the moment P0255 was set.
  2. 2
    Clear the code, perform a road test replicating freeze-frame conditions while monitoring live metering solenoid duty cycle and cam/rotor sensor signal for dropouts or spikes.
  3. 3
    Perform a thorough visual inspection of the metering solenoid harness from ECM to pump connector — look for chafing, loose pins, corrosion, and damaged shielding.
  4. 4
    Measure solenoid coil resistance at the pump connector (with ignition off) and compare to OEM specification; a reading outside range or fluctuating under flex/vibration confirms a faulty solenoid.
  5. 5
    Check supply voltage and chassis ground integrity at the solenoid connector with the ignition on; voltage drop above 0.2 V on the ground circuit indicates a poor earth connection.
  6. 6
    Inspect the cam/rotor position sensor for physical wear, carbon buildup, or cracks; measure air gap against specification if accessible.
  7. 7
    If wiring, solenoid, and sensor all test good and the fault recurs, suspect ECM driver-circuit failure and consult manufacturer service data before replacement.

Related powertrain codes

Frequently asked questions

Can I drive with a P0255 code active?

Short-distance driving is generally possible because the fault is intermittent and the engine often recovers on its own, but the unpredictable power loss and stalling risk make extended highway driving inadvisable. Continued operation with a cycling solenoid can also accelerate pump wear.

Is P0255 the same as P0251 or P0252?

No. P0251 is a general malfunction on circuit A, P0252 is a circuit-A low voltage fault, and P0254 is circuit-A high — all persistent conditions. P0255 specifically flags intermittent signal dropouts on the same circuit, which points more toward wiring or connector issues than a failed solenoid stuck in one state.

Does P0255 always mean the injection pump needs replacing?

Not usually. The most common fixes are connector cleaning, harness repair, or solenoid replacement without touching the pump body. Full pump replacement is warranted only if the internal cam or rotor is mechanically damaged, which would also produce other performance symptoms and metal debris in the fuel.

Which diesel platforms are most commonly affected by P0255?

The Dodge Ram 2500/3500 with the 5.9L Cummins 24-valve and Bosch VP44 pump (1998.5–2002) is the most frequently cited platform. The GM 6.5L diesel with Stanadyne DS4 and early Mercedes Sprinter with Bosch VP injection are also known to produce this code.

Disabling P0255 in software

RaceTune can permanently disable P0255 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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