Hi-Tech Model HT-455

I'm trying to  get the above wired in to a 1991 GMC 1/2 ton pickup.  Alarm and sensor seem to work, but door locks - nada.  The alarm system has two leads, that go +12 v for lock/unlock.  Can't seem to figure out how to convert my 5 wire door lock tap-in.  Going directly to the lock/unlock motor does not seem to work in any configuration. 

I must be missing something simple.  No wiring diagram provided with alarm just pinouts that describe unlock as Negative door switch (I/P -) and Positive door switch (I/P+).

Any suggestions ?