P2097Powertrain
System too rich off idle (bank 1)
Where to start
The mixture after the catalyst is too rich. Usually this is not the engine but the catalyst: it has stopped burning off. ⚠️ But before agreeing to replace it, make sure the rear oxygen sensor is healthy — a stuck sensor produces this code with a perfectly good catalyst.
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 thisLean and rich mixture: P2177, P2187, P2195 vs P0171
How the code is built
Letter — the systemPowertrain: engine and transmission
Common or the maker's ownGeneric code, second group
Which part of the engineFuel and air metering, general
Number of the faultThe serial number inside that group — it does not say how serious the fault is
All codes in «Fuel and air metering, general»
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.