What P0404 means
Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx.
How the engine computer detects it
P0404 is the function check of the valve drive: on valves with a position sensor the module compares commanded and actual position, and a persistent deviation means the valve sticks, is coked or its drive is too weak (GM diesel 2018 above 10 %, GM gasoline 2004 above 15 %, both MIL after two trips). Ford calls it control stuck. Saab's V6 diesel deviates and uses P0404 for a short to positive. EGR control is then switched off and the valve de-energized.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- EGR deactivated
- Rough idle or jerking if the valve hangs open
- Diesel: possibly reduced power
Common causes
- Valve coked or stiff Most likely
- Valve drive (motor, gear) worn Possible
- Position sensor in the valve inaccurate Possible
- Supply voltage too low or ground fault Less likely
How to diagnose P0404
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: egr valve, egr valve actuator, egr wiring, engine control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0404 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Dodge Ram 1500 | 2004–2007 | 5 | 56k |
Counts of owner complaints to the NHTSA that mention P0404 (20 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 4
- Auxiliary emission controls
- 04
- Specific fault
Questions drivers ask
Can I drive with code P0404?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0404?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0404 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P0404 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.
Often reported together
Codes that owners mention in the same NHTSA complaints as P0404. They can point to a shared cause, so it's worth checking them together.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.