OBD-II code · Powertrain (generic)
P0731 Gear 1 Incorrect Ratio
When gear 1 is engaged, the measured ratio between the input- and output-shaft speed sensors does not match the expected ratio for that gear. This means the transmission is slipping in gear 1 rather than transmitting power solidly. Causes: worn clutch packs or bands, low fluid level or pressure, a stuck shift solenoid, or a valve-body fault affecting gear 1.
Is it safe to drive with P0731?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likely1st gear clutch pack worn
- PossibleLine pressure low (pump or valve body)
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
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 4–16 h
- Emissions test
- Usually unaffected
- Parts involved
- Transmission Clutch Pack, Transmission Valve Body, Transmission Fluid
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.