new stereo, now pathfinder wont start

[troublencharleston]

I just replaced an aftermarket stereo with a new one on my 97 pathfinder (automatic) and now it wont start. Everything electric will work, lights, new radio, etc., but no sound at all from the engine. I tried jumping it, unhooking the stereo, and trying to start it in nuetral but still nothing. All fuses are intact. Any ideas?

[MaximA32]

Could have done something that enabled the immobilizer function of the security system. Try switching in the old head unit.