Torque converter lockup clutch not engaging as expected — shudder at highway speed or reduced fuel economy.
Common symptoms
- Shudder ~45–55 mph
- Poor highway MPG
- Check engine light
Typical causes
- Failed TCC solenoid
- Low fluid
- Worn torque converter
- Contaminated ATF
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