help with 04 civic

i installed an audiobaun amp into a customers 04 civic. he bought his sub and box elsewhere so the only thing i know is, its a rf punch 18 incher. he kept his stock deck. he wanted the amp under the passenger seat so i had to remove it along with a yellow harness which i believe is for the safety airbag system. so i reconnect the battery and the airbag warning light is now on, and stays on, is there anything i can do or does he need to take this to a honda dealership and have them reset something? also whenever you close his driverside door or hit the armrest the sub will bump once, it wont bump is you hit in the trunk, just the door and only when the radio is on. wtf is going on there, i didnt run any wires on that side of the car, i did connect a rca converter to the front speaker wires behind the radio, could that somehow be related? i guess ill try moving them to the rears but my main consern is that damn airbag light