P0839 OBD II Trouble Code Four Wheel Drive (4WD) Switch Circuit High

How to easily diagnose and repair, and causes of a P0839 electrical code which indicates a high electrical value in the four wheel drive switch circuit.

Symptoms of P0839 OBD II Trouble Code

  • Transfer case stuck in one gear
  • Vehicle will not go into gear at all
  • Transmission shifts harshly
  • 4WD malfunction light illuminated
  • Check engine light illuminated

Common Causes of P0839 OBD II Trouble Code

  • Defective 4WD switch
  • Transfer case malfunction
  • Faulty or damaged wiring
  • Loose or defective control module ground strap
  • Corroded, damaged or loose connector
  • Defective fuse or fuse-able link (If applicable)
  • Defective PCM or TCM

Severity of P0839 OBD II Trouble Code

The severity of this code is normally moderate, but 4WD switch circuit problems may be severe if the transfer case is stuck in low gear which causes unwanted stress on internal transmission and engine components requiring immediate attention. In some circumstances, the vehicle may not move or shift into gear at all.