P0730: OBD-II code P0730 flags an incorrect gear ratio detected — the TCM commanded a specific gear but the input/output speed ratio doesn't match.

Symptoms

• Check engine light is on; transmission may slip, flare between shifts, or feel unresponsive.
• Harsh or delayed shifts, or the transmission may stay stuck in one gear as a protective measure.
• Companion P07xx codes usually identify the specific gear that is failing (P0731 = 1st, P0732 = 2nd, etc.).

Common causes

• Worn clutch packs or bands allowing slippage within the transmission — usually a rebuild is needed.
• A failed shift solenoid stuck in the wrong position, preventing proper hydraulic clutch apply.
• Low or contaminated transmission fluid preventing proper clutch apply pressure.

What to do?

Check fluid level and condition first — top up or change if needed. Read TCM codes for specific gear ratio failures (P0731-P0735). Test individual shift solenoids. Internal transmission repair or a rebuild may be needed if slippage is confirmed.