Need some help about the car got weird

[knighthunter]

My Nissan Altima 2007 2.5S got something really really weird after I disconnect the negative charge of the battery to install my new auto-dimming mirror. First of all, the Service Engine Soon light came on, but I figure out how to turn off by just disconnecting the negative again and it disappeared, but after that 3 things came up. The first is no horn sound when I push the request switch on the door handle. In the manual, they said it will flash and buzz, but I just saw the flash, no horn. Before that , I always heard that. Don't mistake with the horn when you push the fob. Second, the range mode in the display is not correctly. Say I got 100 miles left to ran out of the gas tank, but when I filled up the gas tank, it did not go up immediately like usually it did. It just increased 4-5 per 30s. The third is the air conditioning. It always set to "Air flows mainly from foot outlets" and with the Air recirculation off. I remembered that all car did not have default setting for the air conditioning, and always remember the last setting before the engine offs. I still need to maintain the car on time so I might ask the dealership to check that, but I want some people can give me some advice.

Thanks you all.

[insaneturbo13]

the only one i can comment on is the no horn for the lock stuff.

go up to the car and hold you unlock, and lock, button down for 5 seconds i believe, the car will honk, youve just enabled the horn feature, repeat to turn off.