Search this site, I wired my 2001 with an aftermarket plug into the factory wiring you are talking about and at the time I posted the wiring color code here. I purchased at Canadian Tire (in Canada) a plug with the 7 pin standard and a molded 4 pin beside it. Nice unit, I did it this way because Volvo's unit does not allow for electric brakes. The only thing to remember is to buy a 4 to 3 wire converter that powers from the battery and therefore isolates the car wiring.