What's the 2003 Buick LeSabre body control module location?

There is no single body control module (BCM) on the 2003 Buick LeSabre. Instead, You'll find three distinct modules that together, make up the body control system (BCS) -- You'll have the dash integration module (DIM), the instrument panel module (IPM), and the rear integration module (RIM). While their names do give a bit of a hint as to which components they control, their duties are pretty well segregated. While You may see hints, it's irresponsible to attempt to diagnose a specific module as failed Yourself. I'm a huge proponent of DIY, but this is one case where a mechanic is really better equipped to provide a solution than You are. Instead of the shotgun approach of replacing different modules to the tune of hundreds of dollars each, You really should take the hit and have it professionally diagnosed.