P0259 Code Meaning and Next Steps

First checks take 10 minutes for basic 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 fault appears more when hot, under load, or after rough-road vibration
3
Basic tool needed
Inspect the connector, harness, and fuel line routing for anything that moves or rubs
4
Basic tool needed
If scan data is available, watch whether commanded fuel delivery drops out while the fault is present
5
Basic tool needed
Look for recent filter or pump work that may have disturbed the wiring or introduced air
6
Basic tool needed
Confirm supply pressure and filter condition so you do not miss a real fueling issue

If the code returns

-If the harness movement changes the fault, repair the wiring before replacing the valve.
-If heat makes it worse, the valve or connector is more suspect than the fuel supply alone.
-If the vehicle also loses power intermittently, confirm whether the supply side is dropping out too.

Background

What this code means

P0259 is a generic OBD-II code for an intermittent secondary fuel metering control circuit fault.

The ECU is seeing the alternate metering path work sometimes and fail at other times. Heat, vibration, connector fit, and a valve that is starting to fade are the common reasons.

Diagnosis

Common causes

Most common

Loose connector or wiring

A connector that shifts with vibration can make the signal come and go.

Common

Secondary metering valve starting to fail

The valve may work cold but drop out after heat soak.

Common

Fuel supply instability

A weak supply can make the metering control loop look intermittent.

Possible

Harness routing or chafing issue

A wire that opens and closes with engine movement can trigger the code.

Avoid these mistakes

What not to do

xDo not replace the pump first if the fault changes when the harness is moved.
xDo not ignore intermittent symptoms just because the vehicle may run normally part of the time.

Parts

Parts that may need replacing

PartTypical costNotes

Secondary fuel metering valve$80-$400Relevant when the valve itself is failing intermittently.

Connector or wiring repair$20-$160Often the best fix when vibration or heat causes the dropout.

Fuel filter or supply-side repair$20-$220Worth checking when the supply side is also unstable.

Related OBD codes

P0256

P0256 means the secondary fuel metering control circuit is not behaving as expected.

P0257

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

P0258

P0258 means the secondary fuel metering control signal is reading too high.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0259 was seeded from dtcdb and then expanded around intermittent secondary fuel metering faults, especially loose connectors, harness movement, and heat-sensitive valves.

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

P0259 - The Secondary Fuel Metering Control Signal Is Intermittent or Unstable