P0258

Injection Pump Fuel Metering Control B Low (Cam/Rotor/Injector)

P0258 is a generic OBD-II powertrain diagnostic trouble code: Injection Pump Fuel Metering Control B Low (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
P0258
Group
Powertrain
System
Fuel/Inj
Severity
Critical (limp mode / no-start)
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What P0258 means

P0258 is stored when the ECM detects that the fuel metering control circuit "B" voltage is persistently low — typically below approximately 0.2–0.5 V when a higher voltage is expected for the current operating state. In distributor-type diesel injection pumps such as the Bosch VP44, Stanadyne DS4, or Bosch VP on early Sprinter OM611, this indicates the control signal to the channel-B metering solenoid (or its feedback return) is near ground potential rather than within the normal 0.5–4.5 V operating band. Common causes are a short to ground in the solenoid wiring, a failed solenoid coil that draws excessive current and collapses supply voltage, or an open ground circuit on the ECM side that causes the reference to read artificially low.

A sustained low-voltage condition on the metering circuit deprives the solenoid of its normal control authority. Depending on pump design and the solenoid's default mechanical position, this can result in the pump defaulting to maximum or minimum fuel delivery — either condition is hazardous. On VP44 applications the pump may default toward low fuelling, causing hard starting and severe power loss; on other platforms the solenoid may default open, resulting in uncontrolled over-fuelling and runaway risk.

P0258 typically causes the ECM to activate limp mode immediately, restricting engine RPM and torque to protect the drivetrain from uncontrolled fuelling. Diagnosis should prioritise continuity and short-to-ground testing of the solenoid harness before component replacement.

Common causes

Most-frequently reported root causes when P0258 is logged.

  • 1
    Short to ground in the channel-B solenoid wiring harness, pulling the control signal voltage below the ECM threshold.
  • 2
    Failed solenoid coil with a shorted winding drawing excessive current and collapsing the supply rail.
  • 3
    Damaged or pinched harness where insulation wear has allowed the signal wire to contact the chassis or pump body.
  • 4
    Open ground reference circuit on the ECM output driver causing the feedback voltage to read near zero.
  • 5
    Corroded or water-contaminated pump-side connector creating a low-resistance path to ground.
  • 6
    ECM internal channel-B output driver failure holding the output in a low state.
  • 7
    Injection pump internal wiring fault between the solenoid terminals and the external harness connector.

Symptoms drivers notice

MIL illuminated immediately with limp mode activated and significant RPM/torque restriction.
Hard starting or no-start condition if the solenoid defaults to minimum fuel delivery in the low-voltage state.
Severe loss of power — engine may only idle or refuse to accelerate beyond low RPM.
Possible engine runaway (uncontrolled acceleration) on pump designs where the solenoid defaults to maximum fuel when de-energised.
Visible harness damage, melted insulation, or burning smell near the injection pump connector in short-to-ground cases.

How to diagnose P0258

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve freeze-frame data and note the exact voltage the ECM logged for channel B; confirm the low reading with a digital multimeter at the solenoid connector before proceeding.
  2. 2
    Perform a visual inspection of the full solenoid harness from ECM to pump connector, paying close attention to routing near hot engine components or sharp chassis edges where insulation can chafe.
  3. 3
    With the harness unplugged at the pump, measure resistance from the solenoid signal wire to chassis ground — any reading below approximately 10 kΩ indicates a short to ground in the harness.
  4. 4
    Measure solenoid coil resistance at the pump connector; a reading significantly below OEM specification (or near zero) indicates a shorted solenoid coil requiring pump-side repair.
  5. 5
    Verify ECM supply and ground integrity at the ECM harness connector using the wiring diagram for the specific platform; an open ECM ground will cause all channel signals to read low.
  6. 6
    If the harness and solenoid test good, connect a known-good breakout harness and monitor channel-B voltage live with the engine running to determine whether the low voltage originates in the ECM driver circuit.
  7. 7
    Do not attempt to operate the engine if runaway risk exists on the specific pump variant; confirm solenoid fail-safe position before energising the system.

Related powertrain codes

Frequently asked questions

Why does a low-voltage fault on a single solenoid circuit cause such severe symptoms?

In distributor-type injection pumps, the metering solenoid is the primary mechanism controlling how much fuel is delivered per injection event. If the solenoid cannot be energised to the correct duty cycle, the pump's internal mechanical default position takes over, which may be maximum or minimum fuel depending on whether the design is normally-open or normally-closed. Either extreme causes either a no-start or an uncontrolled RPM rise.

Is P0258 dangerous?

P0258 is one of the more serious fuel metering codes because a stuck-open solenoid can cause engine runaway — uncontrolled acceleration that cannot be stopped by releasing the throttle. On VP44-equipped Cummins trucks the pump typically defaults to low fuel (safer), but the design should be confirmed in the service manual before dismissing the runaway risk. Pull over safely and have the vehicle towed if severe power loss or erratic RPM behaviour occurs.

Can water in the fuel cause P0258?

Indirectly. Water contamination can corrode solenoid winding insulation over time, eventually creating a short inside the pump. More acutely, water in the pump connector causes a temporary short to ground that triggers the low-voltage code. Always drain the fuel/water separator and inspect the pump connector for moisture when diagnosing P0258.

What is the typical repair cost for P0258?

Harness repair or connector replacement is the least expensive fix, typically USD 100–250 in parts and labour. Solenoid or actuator replacement costs USD 150–400 depending on platform. Full injection pump replacement on a Bosch VP44 Cummins application ranges from USD 800 to USD 2,000 for a remanufactured unit plus installation.

Disabling P0258 in software

RaceTune can permanently disable P0258 — 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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