A 95 SL320 was an early OBDII adoptor and is supposed to be fully compliant - which should mean that you can go to Autozone and have the codes read for free. The connector must be within 3 feet of the driver. It also has a 38 pin connector for blink testing - this is under a little cap on the rear engine compartment, passenger side. You should be able to find more on Arthur Dalton's code reader with a search.