P0255 – Injection Pump Fuel Metering Control “A” Intermittent (Cam/Rotor/Injector)

P0255 is a diagnostic trouble code you’ll usually see on diesel engines with electronically controlled fuel systems. It points to a problem in the fuel metering control circuit for injection pump “A,” specifically an intermittent or erratic signal. In plain terms, your ECU isn’t happy with the electrical feedback from the injection pump that meters how much fuel goes to the engine. This can cause hard starting, rough running, or even stalling. If you catch it early, you can often fix P0255 before it causes serious drivability or engine damage.

What Does P0255 Mean?

P0255 stands for “Injection Pump Fuel Metering Control ‘A’ (Cam/Rotor/Injector) Circuit Intermittent (Bank 2 or All).” It’s most common on modern diesel engines that use an electronic injection pump or high-pressure common-rail system. The ECU monitors the fuel metering control signal and expects a stable voltage and feedback pattern. When that signal cuts in and out, spikes, or drops unexpectedly, the ECU stores P0255.

This code usually points to an electrical issue—wiring, connectors, or a failing fuel metering control valve or injection pump sensor—but in some cases, mechanical problems in the pump or contaminated fuel can trigger it as well.

Quick Reference

  • Code: P0255
  • System: Diesel fuel injection / fuel metering control
  • Severity: Moderate to severe (can cause stalling or no-start)
  • Typical Causes: Wiring faults, bad fuel metering valve, failing injection pump, poor connections
  • Main Symptoms: Hard start, rough idle, power loss, MIL/check engine light

Real-World Example / Field Notes

In the shop, I see P0255 most often on higher-mileage diesel pickups that tow or work hard. A common pattern: the truck starts fine cold, but once hot, it misfires under load and sometimes stalls at stoplights. The owner usually reports that it “comes and goes.” Scan data shows the fuel metering command jumping around, and a wiggle test on the harness at the injection pump makes the readings flicker. In many cases, the fix is as simple as repairing a chafed wire or corroded connector instead of replacing the entire pump.

Symptoms of P0255

  • Check engine light on: The MIL comes on and the code stores, sometimes with other fuel system codes.
  • Hard starting: Especially when hot, the engine may crank longer than normal before firing.
  • Rough idle: Unstable or lumpy idle due to inconsistent fuel delivery.
  • Loss of power: Noticeable lack of acceleration, especially under load or going uphill.
  • Stalling: Engine may stall at idle, when coming to a stop, or occasionally while driving.
  • Poor fuel economy: Erratic metering can waste fuel and reduce miles per gallon.
  • Surging or hesitation: Vehicle may surge forward or hesitate as the fuel metering signal cuts in and out.

Common Causes of P0255

Most Common Causes

  • Damaged wiring to the injection pump: Chafed, rubbed-through, or oil-soaked harnesses near the pump or rail are a top cause of intermittent signals.
  • Corroded or loose connectors: Moisture and road salt can corrode the plug at the injection pump or fuel metering valve, causing poor contact.
  • Failing fuel metering control valve (quantity control valve): The internal solenoid can become sticky or weak, causing erratic current draw and feedback.
  • Internal injection pump wear: High mileage or contaminated fuel can cause mechanical wear that shows up as electrical irregularities in the pump’s control circuit.
  • Low system voltage or weak battery: On some vehicles, low voltage during cranking or heavy load can cause the ECU to see the metering signal as unstable.

Less Common Causes

  • Faulty ECU/PCM driver circuit: Rare, but a bad internal driver or circuit board issue in the control module can cause intermittent control of the metering valve.
  • Poor engine or chassis grounds: High resistance in ground straps can create voltage drops that disturb sensor and actuator signals.
  • Previous wiring repairs: Poorly crimped butt connectors, twisted-and-taped wires, or incorrect splices can fail over time and cause intermittent faults.
  • Water intrusion: Flood damage or leaks can let water into harness connectors or the pump area, leading to intermittent shorts.
  • Aftermarket tuners or modifications: Aggressive tuning or piggyback modules that alter fuel control signals can confuse the ECU and trigger P0255.

Diagnosis: Step-by-Step Guide

To diagnose P0255 correctly, you’ll want a good scan tool (preferably with live data and Mode $06), a digital multimeter, basic hand tools, contact cleaner, and access to a wiring diagram for your specific vehicle. A lab scope is a bonus for watching the control signal, but not absolutely required for a home mechanic.

  1. Confirm the code and check for companions. Connect the scan tool, read all stored and pending codes, and note any related fuel or voltage codes (P0251–P0254, P0087, etc.). Freeze-frame data will tell you when P0255 set (RPM, load, temperature).
  2. Perform a visual inspection. Open the hood and inspect the wiring harness to the injection pump and fuel metering valve. Look for rubbed-through insulation, oil saturation, broken conduit, or connectors that are loose, green with corrosion, or full of dirt.
  3. Wiggle test the harness. With the engine idling and the scan tool on live data (fuel metering command/feedback), gently move the harness and connectors near the pump. If the readings or idle quality change, you’ve likely found an intermittent wiring issue.
  4. Check power and ground at the metering valve. Using a wiring diagram, back-probe the connector and verify proper battery voltage and ground with the key on/engine running. Any significant voltage drop or unstable reading points to wiring, fuse, or ground problems.
  5. Measure resistance of the metering valve. With the connector unplugged and key off, use a multimeter to check the solenoid’s resistance and compare it to spec. An open circuit, short, or out-of-range reading means the valve is faulty.
  6. Inspect battery and charging system. Test battery voltage (engine off and running) and alternator output. Weak batteries or unstable charging can cause intermittent fuel control issues, especially during cranking.
  7. Check for fuel contamination. If you suspect bad fuel, drain a sample from the fuel filter or water separator. Look for water, rust, or debris that could damage the pump or cause sticking components.
  8. Use Mode $06 or advanced data if available. Some scan tools can show you specific test results for the fuel metering circuit. Look for tests related to injection pump control or quantity control valve performance for borderline failures.
  9. Perform continuity and short-to-ground tests. If the problem still isn’t clear, disconnect both the ECU and pump connectors and check the wiring between them for continuity, short to ground, or short to power.
  10. Consider pump or ECU testing last. Only after wiring and the metering valve check out should you suspect a failing injection pump or ECU. At this point, professional bench testing or replacement may be needed.

Pro tip: On many diesels, the harness near the injection pump is tightly routed and can rub on brackets. Take your time inspecting this area; a single exposed wire strand touching metal can cause an intermittent P0255 that’s very hard to catch on a quick glance.

Possible Fixes & Repair Costs

The right repair depends on what you find during diagnosis. In many cases, you can fix P0255 without replacing the entire injection pump. Typical repairs include:

  • Repairing or replacing damaged wiring/harness: Splicing in new wire, repairing chafed sections, or installing a new sub-harness.
  • Cleaning or replacing corroded connectors: Using contact cleaner, terminal repair kits, or new connectors.
  • Replacing the fuel metering control valve / quantity control valve: Often bolted to the injection pump or high-pressure pump body.
  • Replacing the injection pump: Necessary if internal mechanical or electrical failure is confirmed.
  • Battery or alternator replacement: If low or unstable voltage is part of the problem.

Repair costs vary widely. Simple wiring or connector repairs at a shop might run $100–$300. Replacing a fuel metering valve typically falls in the $250–$600 range parts and labor. A full diesel injection pump replacement can easily cost $1,200–$2,500+ depending on the vehicle, pump type, and labor time. Factors that affect cost include vehicle make, parts availability, labor rates in your area, and whether other components (filters, lines, seals) are replaced at the same time.

Can I Still Drive With P0255?

You can sometimes drive with P0255 for a short period, but it’s not recommended. Because this code involves intermittent fuel metering, your engine may run fine one minute and stumble or stall the next. That can be dangerous if you’re merging, towing, or in heavy traffic. Continued driving with an unstable fuel control signal can also stress the injection pump and other components. If the truck still runs, drive it gently and schedule diagnosis as soon as possible; if it’s stalling, have it towed.

What Happens If You Ignore P0255?

Ignoring P0255 can turn a relatively minor wiring or valve issue into a major repair. Over time, erratic fuel delivery can cause hard starting, frequent stalling, excessive smoke, and potential damage to the injection pump or injectors. You also risk being stranded when the intermittent fault becomes a hard failure and the engine won’t start at all.

Need wiring diagrams and factory-style repair steps?

Powertrain faults often require exact wiring diagrams, connector pinouts, and guided test steps. A repair manual can help you confirm the cause before replacing parts.

Factory repair manual access for P0255

Check repair manual access

Compare nearby pump injection trouble codes with similar definitions, fault patterns, and diagnostic paths.

  • P0260 – Injection Pump Fuel Metering Control “B” Intermittent (Cam/Rotor/Injector)
  • P0259 – Injection Pump Fuel Metering Control “B” High (Cam/Rotor/Injector)
  • P0258 – Injection Pump Fuel Metering Control “B” Low (Cam/Rotor/Injector)
  • P0256 – Injection Pump Fuel Metering Control “B” (Cam/Rotor/Injector)
  • P0254 – Injection Pump Fuel Metering Control “A” High (Cam/Rotor/Injector)
  • P0253 – Injection Pump Fuel Metering Control “A” Low (Cam/Rotor/Injector)

Key Takeaways

  • P0255 means the ECU is seeing an intermittent or unstable signal from the injection pump fuel metering control circuit.
  • It’s most common on diesel engines and often tied to wiring, connectors, or the fuel metering valve itself.
  • Symptoms include hard starting, rough idle, power loss, and possible stalling.
  • Thorough diagnosis should start with visual inspection and basic electrical checks before replacing expensive parts.
  • Driving with P0255 is risky, and ignoring it can lead to costly injection pump or injector damage.

Vehicles Commonly Affected by P0255

P0255 shows up most often on modern diesel vehicles with electronically controlled injection pumps or high-pressure common-rail systems. In the real world, you’ll frequently see this code on:

  • Ford Power Stroke diesel pickups and vans
  • GM/Chevrolet Duramax diesel trucks
  • Dodge/Ram Cummins-powered pickups
  • Volkswagen and Audi TDI diesel cars
  • Mercedes-Benz CDI/BlueTEC diesel vehicles
  • Various diesel SUVs and light commercial vans (Sprinter, Transit, etc.)

That said, any diesel with an electronic injection pump or metering valve can potentially set P0255 if the control circuit becomes intermittent.

FAQ

Can P0255 clear itself?

Yes, if the intermittent fault doesn’t reoccur for a number of drive cycles, the ECU may turn off the check engine light and move P0255 to history. However, the underlying problem usually comes back, so you should still inspect and repair the cause rather than relying on it to “fix itself.”

Is P0255 always caused by a bad injection pump?

No. While a failing pump can cause P0255, wiring and connector issues are more common. Many pumps get replaced unnecessarily because the harness wasn’t checked carefully. Always test the wiring, power, ground, and metering valve resistance before condemning the pump.

Can I fix P0255 myself at home?

If you’re comfortable with basic electrical testing and have a decent scan tool and multimeter, you can often handle the initial diagnosis yourself. Simple fixes like repairing a chafed wire or cleaning a corroded connector are very doable at home. Pump or metering valve replacement may require more advanced tools and procedures.

Does P0255 mean I have bad fuel?

Not necessarily. Bad or contaminated fuel can contribute to injection pump wear or sticking components, which might trigger P0255, but the code itself is focused on the electrical control circuit. It’s smart to check fuel quality and filters, but don’t assume fuel is the only cause.

How urgent is it to fix P0255?

You should address P0255 as soon as possible. While the vehicle may still run, the risk of sudden stalling, poor performance, and long-term pump or injector damage makes it a priority. Early diagnosis often keeps the repair simpler and less expensive.