Where is Sensor #2

We are getting a message on the computer that says the
"Bank 1 Heat sensor (Sensor #2)" needs to be changed on my 1996 Bonneville. Where is it? Cannot find it!
Help!!

Thanks,
Donna

Can you post the code from the computer? This sounds like the rear O2 sensor but I can't be sure without the code. If it is the O2 sensor it would be the one behind the cat.

I forgot to tell you that it is a 1996 Bonne.
Yeah, that is the one, but when my mechanic looks there, he cannot find it. Is it "hidden" somewhere behind something? or in something?

It is in the exhaust pipe, directly behind the catalytic converter. It comes out horizontally toward the passenger side of the car.