I've done pretty much a total full tune up to my brothers 2004 with the 4.2L Heritage V6, he is asking me to do the O2 sensors, I am having trouble finding out if there are 2 or 4 sensors.
Anybody have any idea?

 

Dual cats have 4 sensors, 2 upstream, 2 downstream.

Of course you could crawl underneath and count them.

 

Aye, there was not enough beer in the house to allow me to crawl under there Mike, lol
I thought about it, but I had just got done changing out the plugs and wires.
Since there are 4 he may say screw it, but if he gets them I'll gladly put them in for him.

Thanks for the response Mike, hope all has been well!

 

Any suggestion for replacement sensors?
I see Bosch listed as OE..

If my bro gets them he is considering BOSCH15717
But if there is a decent cheaper part he would go that route as this is not really a daily driver, it is just a backup truck which he is letting me drive while I work on my Grand Prix..

I found this pic, posting in case it will help others in the future.