After 5 years my original cat probe was faded and nearly impossible to see where the active zone was. I had a fairly good idea but contacted my local dealer and purchased a new one for $48. What a difference in cat take off time. My steel cat was active in half the time it usually takes from a cold start. Does the temp prob wear out? I periodically cleaned my original one. I viewed the new floor models and the new princess and kings have a longer cat probe. The one I purchased is the original.