What it means
The transmission control module detected that the actual transmission gear ratio does not match the expected ratio. The code does not specify which gear is affected or identify the cause.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The TCM uses transmission input and output speed signals to check whether the actual ratio matches the ratio expected for the commanded gear. P0730 sets when that comparison is outside the allowed range, without identifying a particular gear.
Common causes
Most likely first.
- Internal slippage
- Valve body fault
- Speed sensor reading inaccurate
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Record freeze-frame data and all transmission codes to identify the vehicle speed, load, and commanded gear when the mismatch occurred.
- Check transmission fluid level and condition according to the vehicle's specified procedure, looking for evidence of low fluid or wear.
- Inspect input and output speed sensor connectors and wiring for damage, contamination, loose pins, or poor contact.
- Compare commanded gear with live input and output speed data during a controlled drive, noting when the ratio diverges.
- Test sensor signals and circuits against the manufacturer's specification, then investigate hydraulic pressure, valve-body operation, and internal clutch slip if the readings are credible.
Common fixes
- Correct low transmission fluid or service degraded fluid as specified for the vehicle.
- Repair damaged speed-sensor wiring or connector contacts.
- Replace a speed sensor only if its signal or circuit test is faulty.
- Repair a confirmed valve-body or hydraulic pressure fault.
- Repair worn internal friction elements if testing confirms transmission slip.
Can I keep driving?
Avoid towing, hard acceleration, and long trips if the transmission slips, shudders, or enters limp mode; have it checked promptly. Continued driving with a ratio fault can overheat the fluid and increase internal transmission damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.