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.

Real-world scan data

Seen in

415

scans in the past year

Found in

0.1%

of scans

0.1%

of scans that found faults

Appears alongside · share of P0731 scans

P0732in 58.5% of scans

P0733in 48.9% of scans

P0734in 37.6% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P0731 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX