P0738
System
Powertrain (Transmission)
Scanner required
Full-system scanner (engine, ABS, SRS, transmission, service resets)

Gear 8 Incorrect Ratio

Understand P0738, common causes, and the right SEAFLO pump to diagnose it.

Eighth gear ratio incorrect on 8–10 speed automatics.

Common symptoms

  • Missing top gear
  • Reduced fuel economy

Typical causes

  • Failed 8th gear clutch
  • TCM calibration issue
  • Low fluid
  • Solenoid sticking

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

Frequently asked questions

Can I diagnose P0738 with a basic code reader?
P0738 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 P0738?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.