P0191Powertrain
Fuel rail pressure sensor — reading out of range
Where to start
The rail pressure sensor is reading outside the expected range. Before replacing it, watch the pressure live at idle and on a throttle blip: a flat line with no reaction means a lost contact more often than a dead sensor.
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 thisFuel pressure: codes P0087, P0088 and P0089
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 «Intake measuring sensors»
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.