2002 Monte carlo LS Does magic?

I got a 2002 Monte Carlo LS back in october i had to replace the intake manafold gaskets......now when i got it up and running and had the battery disconected for more than 12 hours the door locks do tricks...... When, i start the car the doors go, lock-lock-lock-lock-lock-lock-lock..intel i hit the the brake then the go unlock-unlock-unlock-unlock. then when i put the car into drive it locks over and over again.... it will keep doing it u just have to listen cause it gets real quite but when i hit the gas or brake it starts up loud again...... i do have a after market radio and system in the car but it didnt do it before with it in there i might just bring it to chevy and ask them to reprogram it but thats probily bout $100 ........now if ANYbody has any ideas please help this is extermly annyoing promblem email me at [email protected]