Transmission · Powertrain · generic (SAE-defined)
P0730: Incorrect Gear Ratio
P0730 means the transmission computer found that the speed ratio between the input and output shafts does not match any expected gear, a general sign of slipping or sensor error.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0730 sets
The transmission control module (TCM) continuously calculates the ratio of input speed to output speed and compares it with the ratio of the commanded gear. When the measured ratio does not match for a set time, it sets P0730, sometimes along with a gear-specific code. On transmissions without an input sensor, engine speed may be used instead. Limits are manufacturer-specific.
Common causes of P0730
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Low or burnt transmission fluid
- Worn clutch packs or bands
- Faulty shift solenoids or pressure control solenoid
- Clogged filter or weak pump reducing line pressure
- Faulty input or output speed sensor
- Valve body wear or sticking valves
P0730 symptoms
- Check engine light on
- Slipping or engine speed flaring
- Delayed engagement into drive or reverse
- Harsh or erratic shifts
- Limp mode or stuck in one gear
How P0730 is diagnosed
- Read all transmission codes, including gear-specific ratio codes, and record freeze frame data
- Check fluid level, smell and color
- Road test while watching input, output and engine speed in each gear to find which gear slips
- Verify speed sensors read accurately
- Check solenoid operation and line pressure
- Inspect pan debris and consider internal inspection if wear is evident
Typical fixes for P0730
- Correct the fluid level or service fluid and filter
- Replace faulty solenoids or speed sensors
- Repair or replace the valve body
- Rebuild or replace the transmission if internal parts are worn
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P0730 FAQ
What does code P0730 mean?
P0730 means the transmission computer found that the speed ratio between the input and output shafts does not match any expected gear, a general sign of slipping or sensor error. The standard definition is "Incorrect Gear Ratio."
Can I drive with a P0730 code?
Keep driving to a minimum. A transmission that is not holding a gear can overheat and damage clutches quickly, and some vehicles will go into limp mode.
What is the difference between P0730 and P0731 through P0735?
P0730 is a general ratio fault, while P0731 through P0735 and P0729 identify the specific gear where the mismatch was found.
Can a fluid change fix P0730?
If the fluid was low or degraded, restoring it can help. If clutches are already worn, a fluid service alone will not repair the slipping.
Keep researching
More transmission codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.