P0790 OBD II Trouble Code Normal/Performance Switch Circuit Malfunction

How to quickly diagnose, repair, and info on symptoms and causes of a P0790 code that shows a malfunction in the transmission normal / performance switch circuit.

Symptoms of P0790 OBD II Trouble Code

  • Mode switch inoperative
  • Erratic and/or abnormal switch operation
  • Inefficient shift pattern
  • Low power
  • Not downshifting when torque is needed

Common Causes of P0790 OBD II Trouble Code

  • Defective or damaged switch
  • Corrosion causing high resistance (e.g. connectors, pins, grounds, etc.)
  • Wiring issue (e.g. frayed, open, short to power, short to ground, etc.)
  • Defective shift lever
  • TCM (Transmission Control Module) issue
  • Fuse/box issue

Severity of P0790 OBD II Trouble Code

I would say this is set to low severity. That said, you may want to avoid spirited or hard driving. This may cause you to be putting unneeded stress on the transmission and it's components so be common sensical here.