OBD-II · Engine and powertrain (P)
P0404
EGR control range/performance
What it means
The EGR valve position does not follow what the engine computer commands, usually because the valve is sticking.
Symptoms
- engine warning light
- possibly reduced power (limp mode)
- rough idle or hesitation
- more smoke than usual
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | carbon build-up making the valve stick |
| 02 | worn actuator |
| 03 | EGR position sensor fault |
| 04 | high resistance in wiring |
| 05 | vacuum supply fault on vacuum-operated valves |
What to check, step by step
- 01Compare commanded and actual EGR position in live data.
- 02Run the actuator test and listen/feel for smooth movement.
- 03Remove the valve, clean carbon from the valve and seat.
- 04Replace the valve if it still does not follow commands.
- 05Some cars need an EGR adaptation after fitting.