Diagnostic Rules

  • A cleared check engine light leaves internal I/M Readiness monitors in an 'Incomplete' or 'Not Ready' state.
  • If EVAP, Catalyst, or O2 monitors show 'Not Ready', assume a fault code was cleared within the last 15 miles.
  • Carry a handheld bidirectional OBD-II scanner capable of reading permanent (non-clearable) DTCs.

Disreputable sellers frequently clear trouble codes 20 minutes before driving a car onto the auction block. Knowing how to read internal ECU readiness monitors protects your wallet from expensive catalytic converter replacements.

"Wholesale dealer auction access allows independent operators to purchase inventory 15% to 30% below retail book value, bypassing dealership markups entirely."