Looks like 1 o2 sensor on the rear manifold and 1 near the cat converter (1997 LS 3.1.) Which is what...Regards...Tom H

 

i will check when i get to work, to make sure, but there should be 2 on there 1 pre cat and 1 post cat

 

everyting in the US 96 and newer has aleast 2, depends on the engine type and how the exhaust is set up, but atleast 1 pre cat, and atleast 1 post cat

if there is only 2 typicly the one on the manifold will be called sensor 1 bank one, and the one after the cat will be sensor 2 bank 1.

 

yep.

the second O2 is there to make sure the cat is working. thats its only job.

 

my computers say 1 before cat and 1 after cat


before cat part # is 21539
these are ngk part #'s
after cat part # is 21016

now if there is 2 before the cat that it would just be 2 of the 21539 o2's, but my computer only shows 1