According to the Bentley, all 2000 and up have the precatalytic converters with pre and post O2 sensors.
I'm not up to speed on emissions, but I believe the sensors are required on 1 cat on each side. I don't see any on the rear cats, so maybe if you have them on the rear cats, they won't be on the precats?
This is definitely strange...
1997-1999.
2000-2004.
