P0603Powertrain
Internal control module keep alive memory error
Where to start
A keep-alive memory error — the memory that holds settings with the ignition off. The classic footprint of a disconnected terminal or a flat battery. Learned adaptations are usually lost with it, and the car drives slightly differently for the first few trips — that is normal.
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 thisControl unit faults on itself: P0600, P0601, P0603, P0606
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 engineControl module and its circuits
Number of the faultThe serial number inside that group — it does not say how serious the fault is
All codes in «Control module and its circuits»
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.