That fat aluminum one on the left if for the ABS, the black one on the right is for the engine (at least, that's what I thought it was). I also have an 'extra' EPA black box in my harness, though.

Does your vehicle have O2 sensors?

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A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608

Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL.