When the wiring fails, all kinds of spurious faults occur. Some mechanics refuse to do such diagnostics unless the engine wiring harness is first replaced. Also, the shorts from this bad wiring can damage other expensive electrical components, so it is in your best interest to replace the original wiring harness that has crumbling insulation with a new harness. It's not a question of IF the wiring harness needs to be replaced, but when.

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95 E320 Cabriolet, 169K