Parts
$50–200
P0404 — Exhaust Gas Recirculation Circuit Range/Performance
SAFEIs it safe to drive? EGR isn't responding as commanded — emissions issue, drivable, but schedule a diagnosis before your next inspection sticker is due.
What P0404 means
The ECM commanded the EGR valve to a specific position and the position sensor reported back something different. This is a 'rationality' fault — the parts are talking to each other but the answers aren't making sense, which usually points to a dirty or failing valve.
Most likely causes (in order)
- EGR valve clogged with carbon deposits (clean passages and pintle before replacing)
- EGR position sensor worn or contaminated
- Valve pintle sticking from carbon — moves but not freely
- EGR cooler clogged (on diesel and some gas engines)
- Wiring fault on position feedback circuit
Symptoms you might notice
- rough idle
- hesitation at light throttle
- possible stall
- failed emissions test
What to check first
Command the EGR valve to 50% open on a scan tool and watch the position sensor readback — if commanded position and actual position diverge by more than about 10%, the valve is mechanically sticking. Clean first with aerosol throttle body cleaner, then retest.
Repair cost & difficulty
Labor
0.5–2 hr
Difficulty
DIY-friendly