Where is the Battery at on a 2001 Pontiac Bonneville??

Under the rear seat.

And welcome to the club.

Ok thank you very much. Im sorry i feel like an idiot an im sure its a stupid question...but i just got the car and havent relly messed with it much yet. Thanks again.

Not a problem. It'* a stupid place to put it.

Lets see some pictures.

It'* on the passenger side under the rear seat. Lift up on the front of the seat bottm and the seat lifts right off.
Welcome to the club.
What kind of issues are you having?

Not to sound like a tool but, it says where and how to access the battery in your owners manual. If you don't have one, you're forgiven.

If you need a new one, be prepared to pay $130 for it. That'* NOT at the dealer either.

If that is the case. We have them right here.
https://www.gmforum.com/t285036/

...and they are FREE!!!!!!

My Service Engine Light came on and i was gonna try and unplug the battery and reset the computer just to see it it is something little or if it will come back on, before i take it to the mechanic.

Take it to AutoZone/Advance/O' Reilly to get the code pulled for free.