P078A OBD II Trouble Code Shift Timing Solenoid B Malfunction

How to easily diagnose, repair, and symptoms and causes of a P078A code that indicates a detected malfunction with the B shift timing solenoid.

Symptoms of P078A OBD II Trouble Code

  • Stuck in gears
  • Erratic shifting
  • Transmission slippage
  • Hard or harsh shifting
  • Inefficient shift timing
  • Poor driveability
  • Poor acceleration
  • Overall poor performance

Common Causes of P078A OBD II Trouble Code

  • Damaged or defective shift timing solenoid
  • Dirty Automatic Transmission Fluid (ATF)
  • Low ATF
  • Obstruction in ATF passages
  • Broken or damaged wiring harness
  • TCM issue
  • ECM issue
  • Pin/connector problem (corrosion, melting, broken lock tab etc.)

Severity of P078A OBD II Trouble Code

I would say this code is moderately severe. If this issue is left unrectified for too long you could cause some serious harm to the transmission not to mention your pocketbook.