Originally Posted by Jhill

I have not used this method to test post cat but I’ve heard it still works even post cat (maybe a slower switch), you can make a vacuum leak and watch all sensors react to it, rears should go low voltage like .1 ish and the fronts for the z I believe (I would need to double check) are a 0-5v with 5 being lean I think. If I remember reading right the nissans are opposite what a conventional o2 is and given in voltage. I found information on them before and they are a little different than some of the other AF sensors but now I cant find it.



Then you can force it rich with a little propane and watch all sensors switch.



Not sure if snap throttle method will work for post cat testing. Just an FYI some manufacturers actually use the post cat for fuel trim as well, some are more open about it than others like Toyota I believe the rear o2 heavily effects fuel trim.