[V8] O2 ground

[Buchholz, Steven]

If you bolt it to anything that has a good electrical connection to the
engine block you are probably OK.  As I noted earlier, Audi did have a
ground specifically intended for the sensor inputs to the ECU ... the
*best* place to ground the OXS is to this exact point on the back of the
engine.  

If you attempt to ground the OXS to anything else you are asking for
trouble ... especially if you have any thoughts of grounding the OXS to
the body of the car.  If that's the only place you can find, I would
strongly recommend that you forget about trying to make a 4-wire work
and go back to a 3-wire and depend on the connection between the engine
block and the exhaust header.  

As others have noted ... each heater wire is as good as any other.  

One thing that I noticed when I recently replaced the spliced in 3-wire
I previously installed on #344 was that those splices got extremely hot
... and were probably compromised ... even with all the proper heat
shrinking and such.  I don't know if Bosch still offers the "Universal"
3-wire sensor ... the last "universal" unit I get from TPC was actually
one that was intended for a specific application ... I hacked off the
connector and spliced my original connectors from the old sensor ...
fortunately there was enough of a cable attached to the new sensor that
I was able to locate the splices away from the exhaust system.  

Steve B
San Jose, CA (USA)
> 
> Hey all,
> While I have the old and new o2 sensors on the bench, hopefully
someone can
> remind me what the general consensus is regarding where to ground the
fourth
> (gray) wire?
> 
> I'm replacing a 3-wire obviously. Also, I presume it doesn't matter
which
> white wire gets spliced with which wire...?