P0730 Incorrect Gear Ratio

P0730 indicates an incorrect gear ratio. The transmission controller sees a mismatch between expected and actual input/output speed relationship.

Code status

Needs verification

Not yet verified against SAE J2012_202509 / J2012DA. Treat unverified rows as a lookup aid, not repair authority.

System: Transmission
Scope: iso-sae-controlled-p0
Standard: SAE J2012 / ISO 15031-6
Source: legacy-import

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not authorize major transmission work from P0730 alone; sensor data, fluid condition, and companion codes must be evaluated first.

Useful checks before replacing parts

Check transmission fluid level and condition where serviceable, then review input speed, output speed, commanded gear, and slip data.
Scan for solenoid, pressure-control, speed-sensor, and range-sensor codes that can explain the ratio error.
Verify whether the fault occurs in one gear, multiple gears, during shifts, or under specific temperature/load conditions.

Related OBD-II codes

These nearby transmission entries can help compare wording and fault area. They may share the same verification status as the source database.