OBD-II Code · Transmission
P0731
Gear 1 Incorrect Ratio
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$500–$3,500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
First gear ratio fault.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Slipping in 1st
Likely causes
- Worn 1st gear clutchMost common
- Solenoid
- Low fluid
Read the full diagnostic procedureP0731 is the gear-specific version of P0730 — the TCM has commanded 1st gear but the actual input-to-output ratio doesn't match what 1st should be (t…
P0731 is the gear-specific version of P0730 — the TCM has commanded 1st gear but the actual input-to-output ratio doesn't match what 1st should be (typically around 2.8-3.5:1 on most automatics). That means 1st gear is slipping, or the wrong gear actually engaged, or a shift-solenoid valve has stuck. Fluid level and color first; burned fluid plus a P0731 on a higher-mileage trans is usually a slipping low/reverse clutch or a failed forward-clutch seal. With the trans in DRIVE at a stop and the brake held, watch input RPM as you brake-torque to ~1,500 RPM (stall test) — input should follow engine RPM closely with minimal slip on a healthy unit. A 200+ RPM gap between engine and input RPM under stall is the smoking gun for converter or clutch slip.
Cheapest external causes to rule out first
stuck shift solenoid A or B (often $50-150 each), a stuck pressure-control solenoid, or a valve-body separator-plate failure (the gasket between the valve body and case can fail and cross-feed pressure between circuits, mimicking internal damage for $300 worth of parts).
Vehicle-specific patterns2001-2007 Nissan Pathfinder/Frontier with the RE5R05A 5-speed throws P0731 from a known 1st-gear clutch pack failure — Nissan TSB and class-action co…
- 2001-2007Nissan Pathfinder/Frontier with the RE5R05A 5-speed throws P0731 from a known 1st-gear clutch pack failure — Nissan TSB and class-action coverage on certain VINs, but past warranty you're rebuilding.
- 2004-2010Toyota Sienna/Highlander V6 with the U151E/U660E 5/6-speed rarely throws P0731 unless fluid was neglected past 100k miles — when it does, the cause is usually a worn 1st-gear band servo, not a hard-part failure.
- 2007-2014Chrysler/Jeep with the 545RFE/65RFE throws P0731 from a failed Underdrive Brake assembly when the solenoid-pack drops pressure — solenoid-pack-first diagnostic order saves customers a rebuild quote about 30% of the time per ATRA bulletins.
- 2005-2010GM 4L60E/4L65E (Silverado 1500, Trailblazer) throws P0731 from a worn 1-2 accumulator piston or a cracked sun-shell — both internal but the sun-shell failure is catastrophic and often produces metal in the pan.
Estimated repair$300 (solenoid pack) to $3,800+ (full rebuild).
Look up another code
P0731 — frequently asked
What does a P0731 code mean?
First gear ratio fault.
What causes a P0731 code?
Common causes: Worn 1st gear clutch; Solenoid; Low fluid.
What are the symptoms of a P0731 code?
Typical symptoms: Check engine light; Slipping in 1st.
Is it safe to drive with a P0731 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $500-$3,500.
How do I diagnose a P0731 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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