99 300m alarm system???

I just bought a 99 300m and it came with a aftermarket auto start. Here's the thing, if you lock the doors and then use the key to unlock the drivers door, the alarm will go off, but if you use the key in the passengers door it will not! it will automatically unlock/lock all doors if you use the key in the passengers door! So I think that the alarm system is not recognizing when the key is in the drivers door, but only when it is in the passengers! The auto start does not work either and I think this door thing is causing the system to not know when to unarm itself! any input would be appreciated!
thanks,
Kalvin