P0404 — EGR Control Circuit Range/Performance

P0404 means the EGR valve isn't moving to the position the ECM commanded. Carbon buildup binding the valve is the leading cause on any engine with real mileage.

Cost range: $100–$700. Severity: medium. Safe to drive? Yes, though driveability and emissions will suffer.

Most common causes of P0404

1. Carbon-seized EGR valve — Cleaning sometimes revives it; often replacement is faster. ($150–$600)
2. Failed EGR position sensor — Integrated into the valve on most modern designs. ($200–$600)
3. Wiring fault to the EGR valve — Heat-damaged connector near the exhaust. ($80–$250)
4. Clogged EGR passages — Valve moves but nothing flows. ($250–$700)

Symptoms drivers report with P0404

• Check engine light
• Rough idle
• Pinging under load
• Failed emissions test