excalibur 1855 tach wire issue

Hi I just installed an Excalibur 1855 remotes start and the omega TD BLADE, on 2001 Oldsmobile Bravada. The issue Im having is that when I finished installing it everything worked fine, the remote start worked. started the truck 10 times worked fine. but after turning the vehicle back to my friend, he started having issues with the remote start the truck will start than after 5 seconds it goes off, than when he brought the car back to me I remote started it and it worked fine for the first couple of times, than again it would start and go off, than I would try again and it would work fine again.
P.S. thinking it might be the bypass I tried it with the key and it would do the same thing again, it would start than after 5 seconds it would go off. could it be the tach wire that's messing up or what do you think it could be???? thank you..

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Aurelio Zamora