code dropped between car key & car ?

we have a fiat bravo s, 1997, 1370cc, we changed the battery & the key will not opperate the engine, we only have one key its a blue one, the red one which is a master key didnt come with the car when we brought it. without replacing the ecu, can we by-pass the immobiliser & if so how ? thanks.

nigel thynne
February 2010