P0730: the gearbox's gear ratio doesn't match what's commanded
For each gear, the gearbox computer expects a specific relationship between how fast the input shaft and output shaft are turning, called the gear ratio. This code means the gearbox computer has measured a ratio that doesn't match any gear it commanded. It doesn't say why the ratio is wrong, only that it is.
You might notice
- The gearbox may shift harshly, slip, or feel like it's struggling to find the right gear
- The engine warning light comes on
- gear ratio
- — the relationship between how fast the gearbox's input and output shafts are turning for a given gear
- gearbox computer
- — the separate computer, distinct from the engine control unit, that runs an automatic gearbox
What the code itself says
P0730 is a powertrain (engine, gearbox and drive system) code, and the 0 after the letter means it is a generic code with a standard meaning.
Grouped here as: Gearbox control — Gear selection, shift quality, fluid condition and the sensors and solenoids the gearbox's own control module reads. That grouping is ours, to help explain the code. The code's official family is the letter at the start.
This page is generic. Your car isn't.
A code on its own only tells you what the sensor saw, not what's actually wrong — and that changes next to your other codes. Read this one together with the rest of your scan and we'll work out what's really going on.
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