I just purchased another 1989 535 project car. Yes, I am a glutton for punishment! I did the stomp test to see if there are any codes and the display only give me a code 1 - not 11 or 111 or 1111, just 1 and does not give the " all codes read" code. Just code one forever.
The car has an automatic transmission and I replaced the battery before (my bad) I started tinkering.
The car has a build date of 11/88.