OBD code P0404

The EGR valve position or response does not match the ECU command.

Estimated severity

Medium

Common symptoms

Check engine light on
Power loss or limp mode
Rough idle or hesitation
Smoke under acceleration
Related EGR codes such as P0401 or P0402

Likely causes

EGR valve sticking from carbon deposits
Faulty EGR actuator
EGR position sensor fault
Connector or wiring problem
Control adaptation outside range after cleaning or replacement

Recommended checks

1. Command the EGR valve with a scanner and compare requested versus actual position.
2. Inspect connector and wiring at the EGR valve.
3. Remove and check the valve if it is mechanically stuck.
4. Carry out adaptation or relearn if required after cleaning or replacement.
5. Check related air-flow and boost data before replacing parts.

What does code P0404 mean?

P0404 indicates that the EGR valve is not moving or reporting position as expected. It may be stuck by carbon buildup, have a faulty actuator or position sensor, or suffer from wiring issues. The result is unstable EGR control, which can increase emissions, reduce power and trigger limp mode.

Try assisted diagnostics