How to replace the BCM on a 2006 sts - 2006 Cadillac STS

Nicole, I google it and the 06 Cadillac STS does appear to have a ignition relay. It will most likely be found in the engine compartment fuse/relay box. Check the attached links,instruction and guides, Good luck
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http://www.rockauto.com/en/catalog/cadillac,2006,sts,4.6l+v8,1432044,electrical-switch+&+relay,ignition+relay,3480
2006 Cadillac STS ignition relay Google Search

The fuse is located under the rear seat in the fuse box.Trunk/valet fuse.

Why you here

You go to a dealers parts dept for parts

Why would someone on the internet have
part #'s ?

Three screws

should be on side of actual throttle body attached to throttle shaft with two retaining screws either torx head,or possibly phillips head screw.unplug sensor and remove screws.install in reverse order.

On this website you find information (diagram, description and location) about fuse boxes in Cadillac STS mk1 (First Generation; 2005 - 2006)

Cadillac STS mk1 First Generation 2005 2006 fuse box diagram Auto Genius

I would reccomend using Prestone Extended Life is a 50/50 mix that is prediluted. But before you replace your fluid i would recommend having it flushed first. Hope it helps.

check the head light glass that it is not cracked, or the seal around the glass is broken, and if the the silver reflector,
is water damaged, it needs to be replaced.

Check the fob battery you might need to replace it, The battery only has about a 3 year life

one under the hood one on the drivers side of the dash