The 5-Wire Mystery

[garfield at pilgrimhouse.com]

On Tue, 10 Mar 1998 23:28:27 -0500, Scott Knight <sknight at mich.com>
wrote:

>Finally I can contribute rather than merely glean information...

>http://userdata.acd.net/lance/sefi8lo.html

Interesting, vewy interesting. The picture of the O2 sensor is EXACTLY
that of the NTK 5-wire sensors used on the VX Civics. I mean
EXACTAMUNDO, right down to the wiring harness, connector, even that
rubber strain-relief midway the cable. Go to any Honda dealer and ask to
see the following O2 sensor part #:
	36531-P07-003
which is for some models of 92-95 VX Civic, but since there are a couple
diff. exhaust manifolds, ask for it by part # rather than car yr/model.

I've been doing some research on this type, and it's apparently fairly
complicated, with a std Nernst cell (normal O2 sensor voltage source),
plus a heater, of course, and another gizmo that makes the magic, a
current-driven device refered to as an oxygen ion pump, that actually
controls the rate that Oxygen crosses the Nernst cell barrier. I'm not
sure, but it seems that in addition to controlling & measuring the
heater, for precise temp control, AND measuring the Nernst potential,
that this ion pump gizmo is also both controlled via a varying current
source, as well as measured as to it's resistance, all of these three
elements having to be orchestrated together by the ECU. Not necessarily
overly complex for the likes of us diy_efi higher lifeforms, heh, but
nonetheless much more than a simple O2 sensor of the last generation.
Bosch's new LSU sensor used in their LA-3 Lambda Meter, is the same
kinda gizmo, with this same "oxygen ion pump" technology. Suffice it to
say a simple op-amp or two isn't gonna quite get it with these new
sensors.

Anyone with a Honda Service Manual for a 92-95 VX Civic that might utter
a clue about how the sensor is wired, like for example, does it plug
into some special box BEFORE it hits the ECU, or does the ECU
control/measure all 5 terminals?

Also, since Scott you have one of these FP wide-band options, maybe you
could say whether the O2 sensor wires directly into the main FP box, or
if some "special" interface electronics comes with the option, and goes
between the sensor and the FP's ECU. Hmmm?

Thanks for any/every bit of info posted on this most interesting topic.
I sure hope Brock can find/get that NTK paperwork. Both the curves and
some hint as to the function of the 5 terminals would be a real boon.

Garfield

P.S. I was told by the Honda parts guy that over the last 2 years, these
NTK sensors have come down from well over $200 to around $130 list.
That's considerably less than the list on a Bosch LSM-11 sensor, which
is apparently simply a very well-refined 4-wire heated type of the
previous generation. At the moment, I'm told that the only way to get a
Bosch LSU sensor is to buy their Lambda meter; it's not in production
cars yet. Sure is alot of secrecy surrounding all of this stuff!