95 Volvo 850 door lock wire?

Hey guys, I've got a remote start/alarm system completely installed on my '95 Volvo 850, however the only wire I can't find is the wire to lock the doors. I've tried all the Yellow/Gray wires in under the dash I can find but to no avail. Correct me if I'm wrong, but if I ground the correct wire, the doors should lock right? That is how it works for the unlock. Any help is much appreciated, I've spent entirely too many hours on this and I'm at my wit's end. Thanks!

I've got a probe voltage tester that illuminates if one end is grounded and you probe either a 6 or 12 volt source. When I ground the one end and then probed the gray/red wire, the doors unlocked, so I assumed that I could use the same method to find the lock wire. This is kind of a primative method, but any other suggestions?

you should use a digital multimeter.  It isn't just the grey/red, yellow/grey htere is also a BROWN / blue you need to pulse<--meter this one by turning the key in the door.  You will need 2 relays and two diodes, you will need to cut the grey/red and yellow/grey.  If you can't figure it out still, let me know and i will try to copy the diagram for you. good luckandrew nickle

Would you please send me the diagram? I have the unlock working by sending the negative pulse to the gray/red, but I didn't have to cut the wire or use a relay, I did use a diode since the wire sends a positive charge when I press the lock button on the alarm remote.