P0402 Exhaust Gas Recirculation Flow Excessive Detected

P0402 means the EGR monitor detected excessive flow. The system is flowing more exhaust gas than expected or the feedback signal says it is.

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 clean or replace parts randomly; excessive EGR can be a valve, control, feedback, or wiring problem.

Symptoms of P0402

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 P0402

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

Check for an EGR valve stuck open, incorrect vacuum control, failed control solenoid, or feedback sensor bias.
Review idle quality, stalling, fuel trims, MAP response, and freeze-frame data from the monitor failure.
Inspect EGR passages and valve seating for carbon that can hold the valve open.

Related OBD-II codes

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