P0405 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 connector
2
Free - no tools
Inspect the sensor connector and harness for corrosion, looseness, or heat damage
3
Basic tool needed
If the valve moves by vacuum or command, check whether the sensor reading changes smoothly with movement
4
Basic tool needed
Notice whether the valve or passages are packed with carbon
5
Basic tool needed
If scan data is available, compare commanded position with actual sensor response before replacing the valve

If the code returns

-If the signal stays low on a known-good circuit, the sensor moves higher on the list.
-If cleaning or moving the connector changes the reading, wiring or connector fault becomes more likely.
-If the code returns after replacement, verify the sensor feed and ground side again.

Background

What this code means

P0405 is a generic OBD-II code for a low-input EGR position sensor fault.

That usually means the ECU is seeing less sensor signal than expected from the EGR valve position side of the system.

Diagnosis

Common causes

Most common

Failed EGR position sensor

The feedback sensor may no longer report a believable low-end value.

Common

Connector or wiring issue

A poor connection can pull the signal low.

Common

Carbon-stuck EGR valve

If the valve cannot move properly, the sensor can read wrong.

Possible

Reference circuit problem

The sensor may be fine but the support circuit is not.

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 side is clearly wrong.

Connector or wiring repair$15-$120Useful if the signal drops or is contaminated.

EGR gasket or cleaning supplies$20-$100Worth checking if carbon buildup is affecting movement.

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.

P0406

P0406 usually means the EGR position sensor is reading too high.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0405 was expanded around common low-input EGR position sensor faults, especially sensor failure, wiring problems, and carbon-stuck 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

P0405 - P0405 Usually Means the Egr Position Sensor Is Reading Too Low