P0402Powertrain
EGR flow excessive detected
Where to start
There is too MUCH recirculation flow. The opposite of P0401: the valve does not close fully, usually because of the same soot. At idle that gives shaking and flat spots, because exhaust goes into the cylinders instead of air.
What to watch in live data
A code is not a diagnosis. It says which check failed, not which part to replace. Clearing it without repair only means the car will report it again in a few trips.
How to put together a report a mechanic will actually read
We have a detailed piece on thisP0401: the EGR valve is cleaned more often than replaced
Step by stepHow to check the EGR valve with live data
How the code is built
Letter — the systemPowertrain: engine and transmission
Common or the maker's ownGeneric code: the same on every car
Which part of the engineEmission controls: catalyst, EGR, fuel vapour
Number of the faultThe serial number inside that group — it does not say how serious the fault is
All codes in «Exhaust gas recirculation (EGR)»
How the app helps
CarScan reads this code from your car through an OBD-II adapter, shows whether it is active now or only stored, names the module that reported it, and puts it into a plain-text report for your mechanic.