There's a couple things that it could be, but I'm almost willing to put money on the notion that you didn't plug in the little toggle switch. That toggle has to be put into it's plug on the 5901 (and all other Viper remote starts) AND in the on position. It's plug is the black 2 pin that should be near a black 3 pin (I think... I don't have one in front of me, so it might be elsewhere... 90% sure though)
If the error you're getting is something like 10 flashes of the parking lights, then that's it.
It could also be your neutral safety switch wiring. Ground it for now to make sure.
It may also depend on your programming of the remote start. i.e. If you have an automatic transmission, the 5901 (and all Viper remote starts) comes pre-programmed for a manual transmission. Look in your instruction manual under programming options for how to change it.
If it's a manual, then you'll need to hook up the tachometer wire (purple/white) in the same plug as the brake (small gauge brown) and hood pin (small gauge gray) inputs. And then 'learn' the tachometer signal (it's easy, just start the car with the key, then press and hold the valet button on the antenna until the LED lights up.)
Hope that helps!