P0406 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 engine starts running much worse, stalls, or the warning light flashes.
!The vehicle begins to overheat, knock, or lose power sharply while the code is active.

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

What to check first

Step-by-step checks

1
Free - no tools
Let the engine cool before checking the EGR valve and wiring
2
Free - no tools
Inspect the sensor connector and harness for looseness, corrosion, or heat damage
3
Basic tool needed
If the valve moves, watch whether the signal changes smoothly or stays stuck high
4
Basic tool needed
Check whether the code appeared after intake or EGR service
5
Basic tool needed
If scan data is available, compare commanded EGR movement with the feedback signal

If the code returns

-If the signal stays high on a known-good circuit, the sensor moves higher on the list.
-If moving the harness changes the reading, wiring or connector fault becomes more likely.
-If the code returns after replacement, verify the feed and signal paths again before buying another part.

Background

What this code means

P0406 is a generic OBD-II code for a high-input EGR position sensor fault.

That usually means the ECU is seeing more signal than expected from the feedback side of the EGR valve, which can happen because of an open circuit, sensor drift, or connector damage.

Diagnosis

Common causes

Most common

Open EGR sensor circuit

A break in the signal path can make the reading go high.

Common

Failed EGR position sensor

The sensor may have drifted or failed internally.

Common

Connector or pin issue

A loose or corroded connector can create a false-high reading.

Possible

Heat-related harness damage

A damaged harness can fail open near hot engine parts.

Avoid these mistakes

What not to do

xDo not replace the sensor or valve first if there is obvious wiring, connector, or vacuum damage.
xDo not ignore drivability changes just because the code sounds like an emissions fault.

Parts

Parts that may need replacing

PartTypical costNotes

EGR position sensor or valve assembly$80-$300Relevant when the feedback signal stays too high.

Connector pigtail repair$15-$120Useful if the plug or pins are damaged.

Harness repair$20-$150Needed if an open circuit or heat damage is found.

Related OBD codes

P0403

P0403 usually means the EGR control circuit has a malfunction.

P0404

P0404 usually means the EGR system is out of range or performing poorly.

P0405

P0405 usually means the EGR position sensor is reading too low.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0406 was expanded around common high-input EGR position sensor faults, especially open circuits, sensor drift, and harness damage.

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

P0406 - P0406 Usually Means the Egr Position Sensor Is Reading Too High