OBD-II code guide
P0402 Exhaust Gas Recirculation Flow Excessive
P0402 means the EGR system appears to be flowing too much exhaust gas.
What it means
Too much EGR flow can dilute the air-fuel mixture and cause idle or drivability problems.
Common symptoms
- Rough idle
- Stalling
- Hesitation
- Check engine light
- Poor acceleration
Likely causes
- EGR valve stuck open
- Control solenoid fault
- Sensor error
- Carbon preventing valve closure
- Vacuum control issue
First checks
- Notice if idle improves when EGR flow is blocked for testing.
- Inspect valve movement.
- Check vacuum control routing.
- Scan commanded versus actual EGR data if available.