horn blows while trying to install new battery. Why?

Cause you didn’t hook up a saver tool into the OBD2 port, so the security system is activated. If your lucky the security shut down procedure will be listed in the owners manual. If not then your stuck with the dealer resetting the system.

Answer not posting

If the security system was active when the battery was disconnected or went dead this can happen. Hook up the battery, horn blaring and everything, then lock and unlock the vehicle with the key fob. I've done this before and it's worked for me. Hope that helps! Jim

i know but im not going to tell you