Originally Posted by PHiZ
Yup, from what I understand (at least on teh 6th gens) you need a Y adapter harness and need to keep your OEM headunit.
Acutally I remember someone saying that the power for the remote entry is pulled from another location on OBD2B civics (99-00) and thusly, you don't need a Y harness. So, that is woth investigaing, but It's unconfirmed.
-PHiZ
Yes, on 96-98 the HU ran the keyless entry. If you plan on keeping the stock keyless and want an aftermarket HU, you need the Y harness so you can keep the stock HU behind the dash. :uber gay: IMO.
I have a 96, but with an aftermarket security system. So that rule doesn't apply to me. When I installed my HU I received the Y adapter from Crutchfield for free so I never knew those Y adapters were so expensive. If you have any other questions, PM me.