P0731
Gear 1 Incorrect Ratio
Transmission controls
Generic OBD-II
High
What it means
P0731 means the transmission computer compared input and output speeds in first gear and found the ratio wrong — the gear isn't holding the way it should, which points to slipping. It usually starts with low or worn-out fluid, a shift solenoid, or internal wear, and because slipping generates heat, it should be addressed promptly.
High
Can I keep driving? Drive as little as possible — a wrong gear ratio means the transmission is slipping, which can overheat and damage it. Have it checked promptly.
Common symptoms
What you'll notice
- Transmission slipping or flaring in first gear
- Harsh or delayed engagement into first
- Reduced acceleration from a stop
- Check-engine light on, sometimes with limp mode
Common causes
Most likely first
- Low or contaminated transmission fluidLikely
- Faulty or stuck shift solenoidCommon
- Valve body fault or internal leakCommon
- Worn clutches or bands (internal wear)Less often
- Input/output speed sensor discrepancyLess often
How to diagnose & fix
Work through it in order
- Check the transmission fluid level and condition first — top up or service if low or burnt.
- Read freeze-frame data and compare input vs output speed to confirm the slip.
- Scan and test the shift solenoids for the 1-2 range.
- Inspect the valve body for sticking or leaks.
- If it persists, internal clutch/band wear is likely — have the transmission inspected.
FAQ
Quick answers
Is it safe to drive with P0731?+
Not really — a slipping first gear generates heat and accelerates internal wear. Drive as little as possible and get it diagnosed before it turns into a bigger repair.
Can I just clear P0731?+
It returns quickly if the transmission is still slipping. The underlying cause — fluid, solenoid, or internal wear — has to be fixed for the code to stay away.
Related codes
Often seen with P0731
Read & clear P0731 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX