door unlock? on vehicle tracking unit

i have installed 5 tracking units on 5 vehicles for my wifes emplorer and he wants the door unlock feature hooked up, they are vp390 tracking units from GPS Techonolgies, now my question is would i be able to just hook into the unlock wire with a relay? i have a relay diagram from the company but not sure if it will work correctly tieing into vehicle's unlock wire in bcm or if i have to hook to unlock wire on lock/unlock motor.

the vehicles are 2 2007 ford e150 vans, 2 2006 dodge grand caravans, and 1 2007 chevy 1500 express.

their relay diagram has a jumper from #85 to #30, #30 to vehicle unlock circuit, #87 to ground, and unlock wire from tracker to #86 of relay.

all the vehicles have negative triggers so will this work for every vehicle?

thanks in advance

thats what im trying to figure out, i forgot to mention that their diagram has a diode between #85 and #86 with the cathode on #85 side, and wondering if i have to diode isolate trigger, the only function of the tracker is to unlock the door/doors from a computer not lock them, also how would i check what size resistor i might need? can i probe the unlock trigger at bcm while pressing unlock to figure out ohms? thanks again for any help, i've installed many alarms and remote starters, but these are the first trackers i have installed so not sure if there wiring is like an alarm or rs unit.

not sure if they require a double pulse, ill have to check this weekend, the company does have 8 other caravans with tracking units but the owner isnt sure if door locks are hooked up, the guy that installed trackers in other vehicles went out of business last year, i looked at one of the other vans but the last guy left a rats nest of wires under the dash, i guess ill have to clean up his wiring and try the door locks to see if they work.

thanks again for any and all help.