P0404: EGR A Control Circuit Range/Performance
P0404 means the engine computer found that the exhaust gas recirculation (EGR) valve is not moving to the position it was told to go to. The car is usually drivable for a short time, but the fault turns on the check engine light, switches EGR off, and should be repaired soon.
You can drive, but get it checked soon
The car normally keeps running with EGR switched off, but if the valve hangs open you may get rough idle or jerking, and on a diesel power may be reduced. Without working EGR the car also emits more NOx, so get it fixed rather than ignoring it.
What it means
The EGR system sends part of the exhaust back into the intake to lower combustion temperature and reduce nitrogen oxides (NOx), a regulated pollutant. P0404 is a performance check of the valve and its drive. On valves with a position sensor, the engine control module compares the commanded position with the actual position. If the two keep differing, the valve may be sticking, clogged with carbon (coked), or driven too weakly. The module then switches EGR control off and de-energizes the valve. Some manufacturers use this code slightly differently. Ford describes it as the control being stuck, and one diesel V6 uses it for a short to positive voltage. The check engine light comes on, and a drive cycle (a set pattern of driving the car's computer needs to re-run its self-tests) is required to confirm a repair.
Likely causes
- Valve coked or stiffVery likely
Carbon buildup from exhaust can make the valve stick or move too slowly to reach the commanded position.
- Valve drive (motor, gear) wornPossible
A worn motor or gear cannot move the valve accurately, so the actual position lags the commanded one.
- Position sensor in the valve inaccuratePossible
If the sensor reports the wrong position, the computer sees a deviation even when the valve moves correctly.
- Supply voltage too low or ground faultLess likely
Weak power or a poor ground can keep the valve drive from working with full strength.
What you may notice
- Check engine light on
- EGR deactivated
- Rough idle or jerking if the valve hangs open
- Diesel: possibly reduced power
What to check, cheapest first
- 1Read the code with a scan tool and note any related codes such as P0403, P042E, P0401 or P0405, then check for stored freeze frame data. · you can do it
- 2Inspect the EGR valve connector and wiring for damage, corrosion, loose pins or chafing. · you can do it
- 3Check the battery and charging voltage, since low supply voltage can cause this fault. · you can do it
- 4Remove the EGR valve and look for heavy carbon buildup that blocks or sticks the valve. Clean it or replace it as needed. · you can do it
- 5With a scan tool, command the EGR valve and compare the commanded position with the actual position reading to see whether the valve or its sensor is at fault. · mechanic
- 6Test the valve motor, position sensor, supply voltage and ground with a meter. After the repair, clear the code and complete a drive cycle to confirm it does not return. · mechanic
Related codes
Frequently asked questions
Can I drive with P0404?+
Usually yes for a short time, since EGR is switched off. Have it repaired soon, and stop driving if the engine runs rough or loses power.
Can a loose gas cap cause P0404?+
No. A gas cap affects the fuel vapor system. P0404 points to the EGR valve, its drive, its sensor, or its power and ground.
Will P0404 pass an emissions test?+
Probably not. The check engine light is on and the code is emissions related, so the car will likely fail until it is repaired and the drive cycle is complete.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10