Somebody correct me if I'm wrong. I thought this problem was limited to engine wiring harnesses of 1993-1995 M104 engines, C280, 300E (3.2 and 2.8), E320, S320.

Check the insulation on the engine wiring harness of your car. You'll have to peel back some of the black covering to see the actual wiring insulation. If it looks 200 years old, then you have to replace the engine wiring harness.

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95 E320 Cabriolet, 169K