Its under the spare tire, and in my case under the air pump for the SLS system. Not hard to remove but a pain in the butt for sure! Before removing it from the car, run to the local auto parts store and have it tested while its still in the car. Saves you about another nasty 10mins of disassembly if it tests good.

__________________
2001 BMW X5 3.0 5spd Sport
-aFe Intake
-E46 Sport seat retrofit with Heat
2007 Mini Cooper S 6spd