P0731 — Gear 1 Incorrect Ratio
Drive with caution — fix soon.
What P0731 means
This code means the transmission computer detected that the actual gear ratio in first gear doesn't match what it expects, usually because the gears aren't fully engaging or the clutches are slipping. It often points to low or worn transmission fluid, a faulty shift solenoid, or wear inside the transmission. Many cases are fixed with a fluid service or solenoid replacement, though severe internal wear can require a rebuild.
Common symptoms
- Check Engine light is on
- Transmission slips or revs high when starting from a stop
- Harsh or delayed shift into first gear
- Car feels weak or hesitant when accelerating from a stop
- Transmission may enter limp mode (limited gears)
Common causes
- Low or burnt transmission fluid
- Faulty or stuck shift solenoid
- Worn clutch packs or bands inside the transmission
- Internal mechanical wear or damage in the gear train
- Failing valve body or internal fluid leaks
Typical repair cost
$150 – $3500
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0731 code?
For short, gentle trips usually yes, but you shouldn't rely on it. A slipping first gear can overheat the transmission and cause much costlier damage, so get it diagnosed soon and avoid heavy acceleration or towing in the meantime.
How much does it cost to fix a P0731?
It depends on the cause. A fluid service or single solenoid replacement might run $150 to $600, while internal clutch or transmission rebuild work can reach $1,500 to $3,500 or more.
Is a P0731 code serious?
It's moderately serious. It won't usually leave you stranded immediately, but it signals the transmission is slipping in first gear, which can progress to major damage if ignored.
Could low transmission fluid cause a P0731?
Yes. Low, dirty, or burnt fluid is one of the most common and cheapest causes. A technician will often check and service the fluid first before assuming internal damage.