P0255Generic code

P0255 Code: Injection Pump Fuel Metering Control A Intermittent (Cam/Rotor/Injector)

The P0255 code means there is a fault in the control of the amount of fuel the diesel injection pump (A) delivers, with the circuit cutting out on and off. It usually causes a loss of power, hard starting or an engine that stalls. A loose connection is the most likely culprit.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$60 to $2,000
Difficulty
Hard
System
Fuel Injection
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0255 code means

On diesel engines, the computer controls how much fuel enters the high pressure pump through a metering valve. Depending on the maker it is also called a volume control valve, a flow control valve, an IMV, an SCV or an MPROP. By controlling it, the computer sets the rail pressure and, with it, the power.

The P0255 code means there are intermittent cutouts in the valve circuit, normally from a loose connection.

The metering valve is a part with very fine tolerances. Dirt, water or metal particles in the fuel make it stick, so it responds late or stays in one position. The typical result is an engine that starts and idles but loses strength or stalls when you accelerate, right when the pump has to increase the flow.

The letter A or B tells the valve or the circuit apart when there is more than one, so check the manual for your engine. Before you condemn the pump, which is expensive, change the filter, drain the water, bleed the air and test the valve.

P0255 code symptoms

  • Loss of power and limp mode.
  • Hard starting, or the engine does not start.
  • The engine stalls at idle or when you slow down.
  • Jerking under load.
  • Check engine light on.

Likely causes of the P0255 code

  1. Metering valve stuck by dirt or water in the fuel. This is the most frequent cause.
  2. Fuel filter clogged or full of water.
  3. Valve connector or wiring.
  4. Air in the low pressure side.
  5. High pressure pump worn. This is less common.

How to diagnose the P0255 code step by step

  1. Compare desired and actual rail pressure at idle, when accelerating and when starting.
  2. Check the filter and the water separator.
  3. Measure the metering valve resistance. A typical value is 2 to 6 ohms.
  4. Check the control signal with an oscilloscope or a multimeter that reads duty cycle.
  5. Check the supply pressure at the pump inlet.

How to fix the P0255 code

  • Change the fuel filter and drain the water.
  • Clean or replace the metering valve. On many models it is sold separately.
  • Repair the wiring if it is damaged.
  • Replace the pump only if the tests confirm it.
  • Clear the codes and check the pressure on a road test.

Technical reference data

  • Metering valve: PWM control, approximate resistance 2 to 6 ohms.
  • Rail pressure at idle: 250 to 400 bar (about 3,600 to 5,800 psi).
  • These are reference values only. Check the manufacturer data for your engine.

Brand-specific notes

This code is very common on the pickups below, which use Denso and Bosch pumps.

P0255 on Toyota

Very common on the Hilux and Fortuner, which use an SCV valve. The Toyota SCV is usually sold separately.

P0255 on Nissan

Very common on the Navara, with Denso and Bosch pumps.

P0255 on Ford

Very common on the Ranger, with Denso and Bosch pumps.

Frequently asked questions about P0255

Can I drive with a P0255 code?
With caution. The engine can stall or lose power all at once, which is risky in traffic.
What is the metering valve?
It is the valve that controls how much fuel enters the high pressure pump. Depending on the brand it is called an IMV, an SCV or an MPROP.
Do I have to replace the pump?
Not always. Many times it is enough to change the metering valve and the filter.
How much does it cost to fix P0255?
Between $60 and $2,000, from a filter or a valve all the way up to a complete pump.
What does the P0255 code mean?
The P0255 code is a generic OBD2 code. The injection pump metering control A circuit cuts out on and off, normally from a loose connection.

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