P0402
Exhaust Gas Recirculation Flow Excessive Detected
- Severity
- Medium
- Driving
- Drivable — book it in
The module measured more exhaust gas recirculation than it commanded. Usually the valve is being held open when it should be closed - often by a flake of carbon on the seat. Exhaust gas in the intake at idle displaces the air the engine needs, which is why this fault tends to show itself as a rough idle or a stall when you come to a stop rather than as a problem at speed.
Possible causes
- CommonEGR valve held off its seat by carbon and unable to close fully
- CommonEGR valve stuck open mechanically
- PossibleFaulty EGR position sensor reporting flow that is not happening
- PossibleControl solenoid stuck energised, holding the valve open
- PossibleFailed diaphragm in a vacuum-operated valve
- PossibleFaulty differential pressure sensor
What you might notice
- Rough or unstable idle
- Stalling when coming to a stop
- Hesitation when pulling away
- Poor running until the engine is fully warm
- Check engine light on
What to check, in order
- Remove the valve and check it seats fully closed. Hold it up to the light - if daylight shows past the seat with the valve shut, that is the fault.
- Clean the seat and the valve face. A single flake of carbon is enough to hold the valve open by the fraction needed to set this code.
- On a vacuum-operated valve, check the valve is not receiving vacuum at idle when it should have none. A stuck solenoid or a mis-routed hose does this.
- Watch the EGR position reading with the engine at idle. It should read closed. A reading showing the valve part-open at idle confirms the fault mechanically rather than electrically.
- If the valve seats correctly and reads closed at idle, suspect the sensor reporting the flow rather than the valve itself.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Auxiliary emission controls
P0400P0401P0402P0403P0404P0405P0406P0407P0408P0409P0410P0411P0412P0413P0414P0415P0416P0417P0418P0419P0420P0421P0422P0423P0424P0425P0426P0427P0428P0429P0430P0431P0432P0433P0434P0435P0436P0437P0438P0439P0440P0441P0442P0443P0444P0445P0446P0447P0448P0449P0450P0451P0452P0453P0454P0455P0456P0457P0458P0459P0460P0461P0462P0463P0464P0465P0466P0467P0468P0469P0470P0471P0472P0473P0474P0475P0476P0477P0478P0479P0480P0481P0482P0483P0484P0485P0486P0487P0488P0489P0490P0491P0492P0493P0494P0495P0496P0497P0498P0499