P0402EGR A Flow Excessive Detected
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P0402 means too much exhaust is recirculated, or exhaust flows although the valve should be closed – CARB explicitly requires a leaking valve to be detected. Ford's DPFE check at idle with EGR off expects no pressure difference above the engine-off value; Ford diesels compare the measured EGR rate with the expected one, GM diesels the fresh-air deviation in the opposite direction. Petrol engines idle roughly or stall, diesels smoke and may lose power.
- What you may notice
- Check engine light on
- Rough idle or stalling (petrol)
- Jerking at part load
- Diesel: black smoke, loss of power
- Likely causes
- LikelyEGR valve stuck open, dirt under the seat
- PossibleFord: DPFE sensor drifting or hose wrong
- PossibleDiesel: air leak between air mass meter and turbo, MAF drift
- RareValve control opens unintentionally
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €100 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.