P0579 OBD II Trouble Code Cruise Control Multi-Function Input A Circuit Range/Performance

How to quickly diagnose, repair, and info on symptoms and causes of a P0579 code that indicates an out of range multi-function input in the A cruise control circuit.

Symptoms of P0579 OBD II Trouble Code

  • Abnormal vehicle speeds with cruise control active
  • Cruise control inoperative
  • Cruise control light illuminated regardless of switch position
  • Cannot set cruise control to desired speed

Common Causes of P0579 OBD II Trouble Code

  • Multi-function/Cruise control switch defective (i.e. stuck, broken, missing, etc.)
  • Wring problem (e.g. chafing on steering column/dash parts, water intrusion, corrosion etc.)
  • Connector malfunction (e.g. corroded pins, broken plastic tabs, swollen connector body, etc.)
  • Fluids/dirt/grime in cruise control button/switch causing abnormal mechanical operation
  • ECM issue (e.g. water intrusion in computer body, internal short, internal overheating, etc.)

Severity of P0579 OBD II Trouble Code

Low severity for almost any cruise control fault, that said there are many exceptions. For the most part though, this fault should not be any cause for serious concern. That said, when it comes to electrical issues, they usually get worse over time. The majority of time, this fault will be moderately affordable to fix.