[V8] O2 sensor

Tony and Lillie tonyandlillie1 at earthlink.net
Fri Oct 1 20:29:02 EDT 2004

I'm not saying the fourt was disconnected ever, rather, I switched mine and 
Zay's cars to 4-wire using the auxilary fan ground on the drivers strut 
tower as the ground for the fourth wire (gray). This cured the "surging" the 
cars both did (mine was worse). My question is why the different grounds 
would give diffierent signals. Also, where the ECU sees the reference to be, 
and how an O2 sensor works.

----- Original Message ----- 
From: "Buchholz, Steven" <Steven.Buchholz at kla-tencor.com>
To: <v8 at audifans.com>
Sent: Friday, October 01, 2004 7:18 PM
Subject: RE: [V8] O2 sensor

... well, if you don't have the fourth wire connected to anything it is
as if there is an open circuit ... I'd expect the ECU would generate
codes to this effect ... but yes, I'd expect your car to run like crap
this way!

Connecting the fourth wire to *any* ground is better than *no* ground
... as was pointed out, one of the OXS heater leads is in fact grounded
... this would not be a terrible place to attach the ground wire ... be
extra careful to determine which pin is grounded because the other gets
power when the engine is running ... this would probably be a bad thing
for the ECU to see as a reference and might well damage the ECU.  This
also fits with the esthetics of building an adapter for the Ford sensor
... the 4-3 wire adapter would then be self contained.

Steve B
San Jose, CA (USA)
> It is an interesting theory, where to ground the fourth wire.
> I'm going to
> get out the MM and check the voltage drop from the block to
> the fan ground
> (in my free time, of course :-) ). However, the car runs
> about 100% better
> since I put the 4 wire in, and Zay has reported the same for
> his car. Both
> use the fan ground for the fourth wire.
> Can anyone explain the theory of why the engine would be
> better if there is
> a voltage drop. The O2 sensor is not connected to the engine,
> but rather the
> ECU, so I don't see the difference anyhow. BUT, if one of you
> can educate
> me, I'd be happy to hear how it works.
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