It is supposed to be the ultimate way to emergency bypass the switch and Window Control Unit by jumpering 12v power directly to the passenger door Window motor, via pins 1 and 2. This would sure beat the heck out of having to pull the door panel off to access the motor connections! I saw a reference that says it is down alongside the side firewall for each door, but I simply cannot find it.
On older 928s, it was an 18-pin connector. On 90 and above, it supposedly went to 12 pin.