P071B OBD II Trouble Code Transmission Mode Switch A Circuit Low

How to quickly diagnose, repair, and info on symptoms and causes of a P071B code that shows a low voltage condition in the transmission mode switch A circuit.

Symptoms of P071B OBD II Trouble Code

  • Mode switch inoperative (e.g. tow/haul mode switch, sport mode switch, etc.)
  • Erratic and/or abnormal switch operation
  • Inefficient shift pattern
  • Low power under heavy load/towing
  • Not downshifting when torque is needed

Common Causes of P071B OBD II Trouble Code

  • Defective or damaged mode 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 P071B OBD II Trouble Code

Severity depends heavily on what mode switch your vehicle's fault is referring to. In the tow/haul switches case, I would say this is set to low severity. That said, you may want to avoid heavy loads and/or heavy towing. This may cause you to be putting unneeded stress on the transmission and it's components so be common sensical here.