Ok, so i finally managed to install an overhead console with DIC, in my 2001 Venture that was not equipped with one when it left the factory.
Actually, electrically speaking, it was pretty easy to do. The main wiring is already there, and I found the DIC connector and wiring taped and attached to the headliner, over the passenger's side. To gain access to the connector, you will have to remove the two retaining clips that secures the sunshades in place. Thoses clips keep the sunshades from rotating freely. You do not need to remove or loosen the 3 main sunshades screws at all. Just the two small clips. Thoses clips are attached to the roof, with only one screw.
Then you will have to reach over the headliner with your hand, to locate the wiring harness, then peel the tape, then pull on the wiring harness, to find the connector. When you have the connector in your hands, it's just a matter of "plug and play", to have the DIC operating.
Next:
If you look carefully, you will find that there is an unused connector (a 3 pin connector, but with only 2 wires), near the windshield washer tank. This connector is used for the outside temperature sensor. However, in my 2001 Venture, there's an extra wiring harness extension that needs to be purchased (about two feet long). You will need this wiring extension to be able to mount the outside temperature sensor in the right place, which is in front of the radiator, on the left side. So you will have to purchase the sensor itself (about $10.00) and the wiring extension harness (about $12.00). Maybe this extra wiring harness is already there on the Pontiac Montana, but in my 2001 Venture, it's not there, so I had to purchase it.
So far, so good, however, there's a catch.....
The new overhead console, with the DIC, is slightly narrower than the old console... which means that the headliner cutout hole, near the windshield, is about 1/8 inch larger, on both sides of the front part of the console (near the windshield), than the original overhead console. This gap is only visible for about an inch long, and the rest of the length of the console is OK, with no visible gap. To plug this gap, i've cut the "U" part of the old console, and managed to make the plastic part thinner, using a sander. I then inserted the thinned part over the new console, to plug the visible hole. It looks like it was done at the factory.
You will have to trim part of the headliner too, so the extended portion of the console can be attached to the central top bracket.
You may not feel too comfortable, doing this headliner trimming to your vehicle, so you may chose to have the console professionnally installed instead.
Yves.