Getting flashing Slow Down upon cold start which turns into solid Slow Down after several minutes of idling. Got error codes P1449 (catalyst temperature bank 2) and P1454 (catalyst protection active bank 2). Cat is definitely not hot. I am trying to determine if I have a bad thermocouple or a bad cat ecu. Can I figure that out just by measuring the resistance of the unplugged thermocouple? What resistance should I see at various temperatures? If one side goes bad, does that mean the other isn't far behind? Should I just replace the cat ecus and thermocouples on both sides? Technistrada has their own cat ecu for $189 and thermocouple for $29 which is a very reasonable price.