P0231Powertrain
Fuel pump secondary circuit — low signal
Where to start
The fuel pump circuit reads low. The relay and the fuse are checked first — they cost pennies. A sign you can hear without instruments: with the ignition on the pump must give a short whirr.
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 thisFan, A/C and fuel pump relays: P0480, P0645, P0691
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: injectors
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: injectors»
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.