What is a "quad driver module"

[1995_riviera]

I´ve had the error codes scanned on my 95 Riviera and they indicated error 640: QDM 1 Fault.
I found out this is a quad driver module, but where is this part, so I can check it?

Thanks, Lutz

[michelq]

quad driver built inside PCM which control several componant such as boost control solenoid,evap purge valve,and tcc solenoid inside transmission

[1995_riviera]

Thank you for the detailed information!
Could the tcc solenoid inside transmission report an error if the transmission oillevel gets low?
I had a supplemental oil cooler installed befopre the error occured...