P0404 Exhaust Gas Recirculation Circuit Range/Performance

P0404 indicates an EGR circuit range or performance problem. The EGR feedback or commanded position does not match the expected operating range.

Code details

Generic OBD-II · P0

System: Emissions
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the EGR valve until feedback wiring and mechanical sticking are both evaluated.

Symptoms of P0404

Check-engine light, often with no obvious change in how the car drives.
A failed emissions test or incomplete readiness monitors.
Sometimes a faint fuel-vapour smell (on EVAP codes).

Common causes of P0404

A worn catalytic converter or an oxygen/air-fuel sensor reading out of range.
EVAP leaks — a loose or failed gas cap, cracked hose, or purge/vent valve.
Exhaust leaks, fuel-trim problems, or a fault in a related monitor.

Useful checks before replacing parts

Compare commanded EGR position with feedback position while the valve is commanded through its range.
Inspect valve sticking, carbon buildup, connector condition, reference voltage, ground, and signal integrity.
Check related MAP, idle, and drivability data because EGR performance faults often affect engine response.

Related OBD-II codes

These nearby emissions entries can help compare wording and pin down the fault area.