Before throwing $154 at a new EHA, I bought this test cable from MB, to determine if my EHA is drawing proper mA.

Correct me if I'm wrong, but apparently #1 connects to the EHA; #2 to the amp meter; #3 is where I'm lost (it's a two pole male connector with a 3rd dummy post). I've read it connects to the engine's wire harness but I've no clue where this connection is.

Can someone familiar with this harness' use please help me out?

TIA!

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-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi