I recently read from a fellow poster that you can check the error code pressing the little button in a device attached to the firewall near the battery for 3 seconds and then release.

The light flashed three times. I tried this a few hours later just to make sure and again it flashed three times.

If someone has a list of error codes for the w201 88' 190E 2.3 CA car, I will appreciate if you post it here, thanks.