P0404 fault code: EGR valve performance problem
Plain-language definition
EGR A Control Circuit Range/Performance
What does it mean?
The EGR valve sends part of the exhaust gas back to the intake side, lowering the combustion temperature and reducing the formation of nitrogen oxides (NOx). The engine computer tells the valve what position to move to and, on many cars, reads where it actually is from a position sensor inside the valve.
P0404 means the gap between the requested position and the measured position has gone outside the expected range, or that the valve responds to commands late and incompletely. In other words, the problem is usually the valve sticking, moving slowly or its position being misread, rather than a broken circuit. On engines with more than one EGR valve or circuit, the "A" in the code's definition tells which one is meant.
If the valve stays open, there may be rough idling, shaking and a loss of power; if it doesn't open at all, there's often no obvious symptom. On some cars the engine computer may limit engine power in this situation.
How serious is it?
It's rated Warning. Causes such as soot build-up can get worse over time; if the valve sticks open, idling and pulling power can be noticeably affected.
Severity is a guide; if the warning light is flashing or you notice symptoms while driving, have the car checked at a workshop.
Common general causes
- EGR valve sticking or moving slowly because of soot (carbon) build-up
- Worn EGR valve or valve motor
- Position sensor inside the valve giving wrong readings
- Intermittent poor contact in the connector or wiring
- Leak in the vacuum supply (on vacuum-operated systems)
The list shows general causes; a workshop finds the actual cause on your car with a check.
Definitions by make
Some manufacturers record the same code under their own wording:
- Fiat
- EGR engine, Electrical fault
- Mitsubishi
- Exhaust Gas Recirculation Circuit Range/Performance; EGR control valve stuck
- Volkswagen
- Exhaust Gas Recirculation (EGR) Open Position Performance
Related codes
How does it appear in the 2dakika report?
EGR A Control Circuit Range/Performance
If the code is read as a confirmed (stored) fault, the report shows it with the "Warning" severity; in pending or past records, codes that don't request the warning light and aren't critical appear as "Info". If the engine computer stored them, the conditions when the fault was recorded (engine temperature, rpm, speed) are shown too.
Read this code with the OBD-X1, and clear it from the app after the repair.
Clearing the code doesn't fix the fault; if the problem persists, the code comes back.