In the exhaust pipe.
Follow the exhaust off the back of the motor and on the exhaust pipe it is the first sensor you come too.
you buy a kit at www.eatmyflames.com
You can replace an exhaust clamp with a new one.
It should ask you if you want to update the game on startup. You must be online for this.
its part of the exhaust system
It should be 2 in
Im the exhaust pipe.
i think its bad catalytic