I won't ever believe someone telling me not to worry about the lower engine harness. My upper was shedding plastic like raindrops. Connectors became "dust" when I pulled on them. The dealer said same thing, usually the upper harness. The best way is to go underneath and check the feed at the alternator and the oil sender, easy to inspect. Mine were brittle and had exposed wiring. The plastic wiring cover is crap but not overly expensive to replace and its not hard to change. Just takes your time and good lift equipment to get underneath. Steve