P0256 Code Meaning and Next Steps

First checks take 10 to 20 minutes for the first checks. No special tools are usually needed for the first checks.

Can you keep driving?

Stop driving if any of these apply

!The vehicle suddenly runs much worse, loses power sharply, or the check-engine light starts flashing.
!There is a strong smell, smoke, overheating, or any symptom that suggests a real-time safety problem rather than a stored code alone.

If the light is steady and the vehicle still drives normally: Often yes for a short time, but it should not be ignored if drivability changes are obvious.

What to check first

Step-by-step checks

1
Safety first
Work on the fuel system only with the engine off and keep sparks, hot surfaces, and open flames away from the area
2
Free - no tools
Check whether the code appears with hard-start, stall, or fuel-starvation symptoms
3
Basic tool needed
Inspect the secondary metering connector and harness for damage or looseness
4
Basic tool needed
Verify fuel filter and lift-pump condition first if the engine is not getting enough clean fuel
5
Basic tool needed
If scan data is available, compare commanded fuel delivery in the secondary circuit with actual response
6
Basic tool needed
Confirm whether the vehicle actually uses a separate secondary metering strategy before replacing parts

If the code returns

-If the secondary valve is electrically okay but response is still wrong, check the supply side and the broader pump control picture.
-If the alternate path shares a harness or fuse, inspect that common feed carefully.
-If the code only appears under one operating condition, focus on the path used in that condition.

Background

What this code means

P0256 is a generic OBD-II code for a secondary fuel metering control range or performance issue.

On systems with more than one metering strategy or valve, the ECU is not seeing the secondary path respond as expected. That can be a valve issue, a supply problem, or a wiring fault in the alternate control path.

Diagnosis

Common causes

Most common

Secondary metering valve fault

The alternate control valve may not be metering fuel correctly.

Common

Fuel supply restriction

A clogged filter or weak pump can make the secondary path behave badly.

Common

Connector or wiring fault

Poor electrical contact can stop the secondary metering circuit from responding properly.

Possible

Air in the fuel system

Air intrusion can make the alternate metering path look unstable or out of range.

Avoid these mistakes

What not to do

xDo not replace the pump first if the secondary path wiring is obviously the problem.
xDo not ignore a clogged fuel filter just because the code names a metering circuit.

Parts

Parts that may need replacing

PartTypical costNotes

Secondary fuel metering valve$80-$400Most relevant when the alternate metering path is the part that is off target.

Fuel filter or supply-side repair$20-$180Worth checking when the engine is not getting clean or steady fuel.

Connector or wiring repair$20-$160Important when the secondary circuit has a bad electrical feed or signal.

Related OBD codes

P0252

P0252 means the fuel metering control circuit is not responding properly.

P0253

P0253 means the fuel metering control circuit is reading too low.

P0257

P0257 means the secondary fuel metering control signal is reading too low.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0256 was seeded from dtcdb and then expanded around secondary fuel metering range/performance faults, with a focus on alternate valves, supply restrictions, and wiring issues.

This guide is written as a generic multi-make reference, so bulletin history, sensor locations, and repair order can still change by manufacturer and engine family.

This is generic OBD-II guidance and should not override vehicle-specific service information. Exact diagnosis and repair steps vary by make, engine family, and model year.

Last reviewed: 2026-04-10

Reference: Open reference

P0256 - The Secondary Fuel Metering Control Circuit Is Not Behaving as Expected