Scott Shotton explains how to create a repeatable diagnostic procedure that covers the bases to make sure all other systems are working correctly before pulling the trigger on a new catalyst on pre-OBD II and OBD II compliant vehicles.
Step 1: Read
Step 2: Are there any codes that interfere?
Step 3: Verify exhaust integrity
Step 4: Verify oxygen sensor operation
Step 5: Verify the engine is running correctly
Step 6: Mode $06 analysis (optional)
The OBD II diagnostic conclusion
