P0174Powertrain
System too lean (bank 2)
Where to start
The mixture is too lean on the second half of the engine — this only applies to V-shaped engines. The causes are the same as for P0171: air leaks, hoses, gaskets. If both banks read lean at once, look for something they share: the intake manifold, the airflow meter, a weak fuel pump.
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 thisFault code P0171: where to start
Step by stepHow to find an air leak using fuel trims
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 engineFuel and air metering
Number of the faultThe serial number inside that group — it does not say how serious the fault is
All codes in «Mixture: lean and rich»
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.