P0731
System
Powertrain (Transmission)
Scanner required
Full-system scanner (engine, ABS, SRS, transmission, service resets)

Gear 1 Incorrect Ratio

Understand P0731, common causes, and the right TOPDON scanner to diagnose it.

First gear ratio does not match commanded — slipping clutch pack or low fluid.

Common symptoms

  • Slipping from stop
  • Flare on 1-2 shift
  • Trans overheating

Typical causes

  • Low ATF
  • Worn 1st clutch
  • Failed solenoid
  • Valve body wear

What scanner do you need?

Full-system scanner (engine, ABS, SRS, transmission, service resets)

Use live data and freeze frame to confirm the fault before replacing parts. ABS, SRS, and network U-codes usually require a full-system scanner.

Diagnostic tips

  • Record freeze frame data when the code first sets
  • Clear the code only after fixing the root cause
  • Check for related pending codes that point to a common issue
  • Verify battery voltage is above 12.4V before chasing sensor codes

Recommended TOPDON scanners

Frequently asked questions

Can I diagnose P0731 with a basic code reader?
P0731 may set in the engine module, but related diagnostics often benefit from an enhanced or full-system scanner with live data and freeze frame.
Is it safe to drive with P0731?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.