You should remove the battery to any vehicle, including your 2003 Bonneville, when storing it. This will help so thw battery doesn't corrode, or die.
If it's like the 2001 Bonneville the battery is under the back seat on the passenger side of the car.
The fuse box and battery are under the back seat on a 2003 Pontiac Bonneville.
under the rear seat cusion
My 2003 Bonneville SE Holds 18.5 Gallons.
Where do you add power steering fluid on a 2003 Pontiac Bonneville?
Great Cars - 2003 Bonneville was released on: USA: 27 June 2005
remove seat, remove neg cable from frame and Pos from battery, remove strap and take out battery.
If that's dollars it is.
You have to take the front passenger tire off and a plate under the wheel well to get to the battery.
Take both cables off. Remove old battery. Put new battery in. Put cables back on.
I have a 2003 bonneville. Its battery is located under the rear seat. If you need to have a jump, or give one, use the positive terminal under a red cap just to the rear of the fuse box under the hood on left side of motor as you stand in front of car. Use a metal engine part for the negative ground for the jump.