P0643 OBD II Trouble Code Sensor Reference Voltage A Circuit High

Symptoms of P0643 OBD II Trouble Code

  • Delayed (or no) transmission engagement
  • Failure of the transmission to shift between sport and economy modes
  • Transmission shifting malfunctions
  • Failure of the transmission to switch between all-wheel and two-wheel drive modes
  • Failure of the transfer case to shift from low to high gear
  • Lack of front differential engagement
  • Lack of front hub engagement
  • Erratic or inoperative speedometer/odometer

Common Causes of P0643 OBD II Trouble Code

  • Shorted (to voltage) circuits and/or connectors
  • Bad sensor
  • Defective PCM or PCM programming error

Severity of P0643 OBD II Trouble Code

The urgency of a stored P0643 depends upon which sensor circuit is experiencing a high reference voltage condition. Accompanying codes must be considered before the degree of severity can be determined.