Transmission

P0731 — Gear 1 Incorrect Ratio

Severity: medium Drive with care, to a shop

What P0731 means

The transmission control unit compares input shaft speed with output shaft speed. In first gear this ratio must stay within a fixed range. When the calculated ratio falls outside that range, P0731 is stored, which usually points to clutch slipping or a hydraulic pressure problem.

Symptoms

  • Slipping when pulling away from a stop
  • Engine RPM flares on the 1-2 shift
  • Harsh or jerky shifts
  • Transmission overheating
  • Check Engine light on
  • Transmission goes into limp mode

Possible causes

  1. Low or degraded automatic transmission fluid (ATF)
  2. Worn first gear clutch pack
  3. Failed shift solenoid
  4. Worn valve body causing pressure loss
  5. Damaged wiring or connectors at the transmission
  6. Faulty transmission range (TR) sensor or switch
  7. Internal mechanical transmission fault

How to diagnose

  1. Scan all codes and freeze frame data, looking for other transmission or engine codes
  2. Check ATF level, color and smell following the procedure for your vehicle
  3. Inspect the transmission harness and connectors for corrosion, chafing and fluid contamination
  4. Test the input and output speed sensors and the range sensor
  5. Check solenoid resistance and command them with a scan tool
  6. Measure line pressure
  7. Check for a software update for the control unit
  8. If needed, drop the pan and look for metal debris or clutch material

Common fixes

  • Add or replace ATF and the filter
  • Replace the faulty solenoid
  • Repair the wiring or connector
  • Replace the speed sensor or range sensor
  • Repair or replace the valve body
  • Rebuild the transmission with new clutches

P0731 on different brands

Ford · manuals
On Ford, P0731:00 is documented for 2024-2025 gasoline engines as incorrect gear 1 ratio; it describes the monitor condition that was detected, not a confirmed failed part.

Questions and answers

What does P0731 mean?

The transmission control unit found that the actual first gear ratio doesn't match the commanded one. Most often it's caused by clutch slipping, low pressure or low fluid.

Can I drive with P0731?

Only for a short, gentle trip, such as to a shop. Slipping quickly damages the transmission, so don't put the repair off.

Will a fluid change fix it?

If the cause is low or old fluid, it can. If the clutches are already worn, a fluid change alone won't solve it.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.