Here's the tach lead I tapped into on my '92 CX and it worked fine.
I'm pretty sure the '96+'s have the same plug. It's an underhood tach test signal for attaching a temporary tach to check idle and whatnot. I just cut the plug and spliced the wire from my autometer to it.
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Andy - Reinstated
Hybrid Forum Moderator
'06 Subaru Legacy Spec B - Stock, for now
'98 Civic EX - CTR headlights and grill, Kosei K1's, for sale
'90 240SX - SR20DET that will never get installed, project car.