Guide to replacing the lower engine wiring harness on a mid 90's SL600 with the biodegradable (soy) wiring problems. V12 models from 1993-1996 had this issue. The harness needs to be partially removed and all 16 gauge wires need to be replaced with quality high temp wires, preferably real 200 degrees Celsius military grade stuff. You need to replace 3 wires that go to the alternator, oil pressure sender, and oil level sensor.
This harness can burn and create a left threatening situation if not addressed.