What P0731 means
The transmission isn't holding first gear properly: in first, engine speed and road speed don't match the way they should, which usually means something inside is slipping. You may notice the engine revving when you pull away while the car is slow to pick up speed. Low or worn-out fluid is the first thing to check, but a worn first-gear clutch is common.
How the engine computer detects it
The transmission module divides input (turbine) speed by output speed and compares the result with the ratio of the commanded gear; a deviation means slip – a clutch or brake not holding, too little pressure – or a wrong gear. Thresholds: Ford more than 30 rpm off for 1.8 s three times (diesel 2023: over 20 % for 12 s), GM's 2006 tables and the Allison 1000 converter slip of 200–230 rpm for 2.25 s after one trip, Saab's Aisin boxes over 20 % twelve times without MIL. P0731 concerns first gear. A 2006 GM table uses a tighter 4 % limit here and caps output speed at 1260 rpm; Saab's 2002 9-5 flags 3 % with the brake released. With a one-way clutch in first, slip shows as slipping when pulling away. On GM manual transmissions it checks the gear position sensor instead.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Slipping or flare in first gear, engine speed higher than expected
- Harsh or delayed shifts
- Limp mode (Aisin: second gear and reverse only), transmission warning
- Check engine light depending on manufacturer
Common causes
- Fluid level too low or fluid worn or contaminated Most likely
- Clutch or brake for first gear worn (linings, piston seal) Most likely
- Sticking shift or pressure valve, leaking valve body gasket, blocked passages Possible
- GM manual transmissions only: gear position sensor faulty or not learned Possible
How to diagnose P0731
- Check the transmission fluid level and condition the way your owner's manual describes; some sealed transmissions need a shop. Dark, burnt-smelling fluid or metal flakes are bad signs.
- Look under the car for transmission fluid leaks and fix them before adding fluid.
- Read the transmission module codes with a scanner that supports your transmission. A basic code reader may miss solenoid or pressure codes that explain P0731.
- Note when it slips: only when pulling away, only when cold, or also in reverse. It helps the shop pin down which part is failing.
- A shop can watch input and output speeds on a scanner and test line pressure. If the first-gear clutch is worn, the transmission needs a rebuild or replacement.
- On some manual transmissions this code checks a gear position sensor instead of slip. A shop can test it and run its relearn.
Vehicles that report P0731 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Ford F-150 | 2011–2015 | 13 | 95k | |
| Ram 3500 | 2022 | 6 | — | |
| Ford Escape | 2014–2017 | 3 | — |
Counts of owner complaints to the NHTSA that mention P0731 (36 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 7
- Transmission
- 31
- Specific fault
Questions drivers ask
Can I drive with code P0731?
Only if it pulls away and shifts normally, and then gently and straight to a shop. If the engine revs without the car moving properly, it's stuck in one gear or it slips on hills, don't drive it: have it towed, because slipping quickly makes the damage worse.
Will my car pass an emissions inspection with P0731?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Often reported together
Codes that owners mention in the same NHTSA complaints as P0731. They can point to a shared cause, so it's worth checking them together.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.