1989 BMW 535 Chimes with key out

Picked a 1989 BMW 535 from a field. Had multiple wiring issues due to mice damage. Have car running and now charging and driving. Newest issue is the car chimes when off (key out) every 45 seconds or so. When it chimes there is no indication anywhere on the display of why its chiming Radio is complaining of missing lock code, when running the brake fluid is low indicates in IP (know how to fix this :) , And the brake pad wear sensor is producing a message. We don't see any other wire damage, just wondering if anybody has any ideas or suggestions for how to find the "beep".

Also I only have 1 key for this car. Is there a chip in this vintage or can you simply find a lock smith that can cut the BMW blanks?

Thanks