599 alarm light

Hi My 599 key decided to stop talking to the car and the yellow key light comes up when u turn on ignition. Done the usual stuff of key battery etc. Is there any way to get the engine ECU reprogrammed to bypass the key through ignition. Tks. Or could it be the alarm battery leak issue? I read that there is a 4 letter numeric code that can be entered by using the accelerator pedal or ignition key but I coukdnt find it in my original hand book kit.