celica with sigma alarm?

i have a celica with a sigma alarm/ immobiliser, had a loose connection on the battery which for some reason caused the immobiliser to lock, have changed batteries on remote, nothin. now remote does nothin, won activate central lockin, set alarm or allow to start. i dont have the pin code. aa couldn fix, nor mechanic i know. is there anythin i can do without the code? or anyway to get the code? any help appreciated. thanks.