2003 gmc yukon xl

im installing an auto page rs-750lcd two way remote start on a 2003 GMC YUKON XL i ve run in to a number of problems, 1- when i cut the starter wire (yellow +) to add a relay for starter kill, i turn the key to the accessory position and the truck will crank back to back with out turning the key to the start position, i connect the starter wire back together and it works normal. 2-the autopage rs-750lcd will not start ive installed a few of these befor but never on a 2003 gmc yukon xl,i used the PAC# DLC2 data bus doorlock interface and i got my wiring info. from bulldogsecurity and it says to use a 555l bypass for passlock 2 witch i did, can someone tell me what i need to do to get this truck stated? is it a defective alarm? is it the data bus interface defective or restricting something? is the 555l defective or the wrong bypass? or is somthing simple that im overlooking ?   

1 - sounds like it's wired wrong but if you've installed 750's before that seems to obvious 2 - what happens during the remote start? like relays click and power turns on to all 3 wires then power to the starter wire but the truck just cranks and doesn't catch. Does it start and then die. Power on ign1-3 but no crank attempt. according to dei.com the 555I if for honda and acura not GM

456g looks to be the correct module off dei site

you need to check your yellow wire is it testing start also your passlock wires are different colors  your 555L will work but your passlock ground reference is black your pac interface should work , i know its a stupid question but have you checked your grounds tj