P0730Powertrain
Incorrect gear ratio
Where to start
The gear ratio is not what was expected: the unit engaged one gear and the car behaves as if in another. Start with the fluid level and condition — the commonest and cheapest cause. If the fluid is black and smells burnt, a change is unlikely to help any more, but it is useful to know that before the garage does.
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 thisTransmission codes: P0700, P0715, P0720, P0741, P0750
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 engineTransmission
Number of the faultThe serial number inside that group — it does not say how serious the fault is
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.