I'd venture to say this is very common now. For example, Microheat Inc. makes the heated washer modules, Invotronics makes switches (and other components), Donnelly, Gentex and Muth make various mirror and mirror systems. Then of course there'* Bosch, Pioneer, Bose and the list continues. TRW Safety Systems has been in the picture for a long time (I had an '82 Parisienne with seat belts made by TRW). Most people may be surprised at how much GM acquires from external sources. Without a doubt, these same vendors will be suppliers for other automakers as well.

Don't forget Alps. They make TONS of the switches on the 92-99, being the most popular is the AL7 seat switches.

What is a Body Control Module and what does it do :?

ROD

Basically, it'* a vehicle computer. In the 2K+ Bonneville there are several, all which work together control virtually every vehicle function from dimming the interior lights to controlling the rear defroster and much much more. Many vehicles only have one. BCM is a more general term but ultimately can refer to a single module or any individual module (even though in multi module vehicles there is a specific reference for each).

In the 2K+ Bonneville, there is:

DIM - Dash Integration Module
Controls headlights and exterior lights, horn, interior incandescent dimming, power moding over the class 2 data bus, steering wheel controls and storage of clock settings.

RIM - Rear Integration Module
Automatic Level Control, fuel door lock control, heated seat controls, rear defogger, retained accessory power, reverse lamps and various interior light functions.

IPM - Instrument Panel Integration Module
Ambient light sensor / twilight delay, front HVAC air delivery and temp control, many interior lamp related functions, input device for T/C and trunk lid switches.

Each of the above modules has functions which I haven't listed, simply because there are so many. The term "Body" refers to anything related to body functions in the vehicle (as opposed to PCM which is powertrain control).

Cool to know all this stuff. The reason I said it was the BCM is also because RockAuto and other sources reference that part number as "Body Control Module" but in actuality it is probably the IPM, which is part of the larger "BCM". Effing acronyms, lol.

Depending on which side of the car you're talking about. The DIM is on the right side, just above the passenger kick panel, the IPM is on the left side in the dash and the RIM is mounted behind the rear seat back.

It would be the DIM then.