[Biturbos4] Cheap O2 Sensors

David Pramanik dap128 at hotmail.com
Mon Dec 15 08:44:13 EST 2003

I have swapped out the forward O2 sensors for the VW ones.  In that case,
the wire on the VW sensor was longer than on the Audi one so I could just
repin the connectors.  For the rear O2 sensors, the Audi wire is longer so
it would be necessary to cut and splice.

-Dave Pramanik

----- Original Message ----- 
From: "Keman" <keman at interwolf.net>
To: <biturbos4 at www.audifans.com>
Sent: Sunday, December 14, 2003 7:11 PM
Subject: [Biturbos4] Cheap O2 Sensors

> I'm not sure if this topic has come up before .. if it hasn't, here is
> interesting info if your precat O2 sensors are popping the dreaded
> "resistance too high B1/2 S1" codes.
> You can spend $180 at the dealer .... or $22. Your choice. The latter is a
> VW part .. and it requires a splice to your existing connector. Parts can
> seen at...
> Now I have seen people report these worked fine for the secondary O2
> sensors.. which I don't really understand. I've had them both out and they
> are different bosch part #'s. I figured they were different calibration
> Damned if I didn't throw the piece of paper away at work where I wrote
> all down. Argh.
> I do know that in VAG I saw a much higher voltage coming from the post cat
> sensors after I uh.. altered the cats, vs. the upstream sensors. 0.95
> downstream vs. around 0.53 volts upstream. It's the same exhaust gasses
> just moved a couple of feet.
> Speculation-- The reason people may report these work well downstream is
> that the ECM is very flexible with what the downstream sensors can report.
> So if they report a lower voltage ... who cares? The heater resistance
> is the same so everything is ok. It just thinks the cats are working very
> efficiently. So the folks running the wrong sensors may never notice any
> problem. And an interesting side effect of this .. is that those sensors
> then become the really, really easy way to eliminate precats and/or run
> aftermarket downpipes. No diode necessary if the new sensors are reporting
> lower voltage than they should be.
> Looks like I get to be test guinea pig if noone here knows... because my
> secondary O2 sensors which are now reporting the proper voltage sans cats
> ... have dead heater elements in them. Strangely, they both show 25.5k
> of resistance after they get all warmed up. A week ago it was just one of
> them. I'm not positive but I suspect that's the extreme end of measurement
> the ECM can make. This dead heater element problem cropped up about a
> ago, before I started playing with the exhaust btw ... it is not related
> the diodes or anything I've done.
> The odd part is, I could have sworn I got a precat O2 sensor heater
> resistance error too not long ago ... so I'm probably going to just say
> it and toss all new O2 sensors on it. At $22 a piece, any improvement in
> mileage would pay for them in a year.
> Also, I've not seen a VW part up close but if it has the normal flat pin
> style leads in the connector just like ours... I probably won't even have
> cut the wires because the connectors can come apart. Most of our plugs and
> pigtails just require a small tool inserted into the little slits and the
> terminals can be extracted ... then they just snap with the wires into the
> old plug. Presto.
> If anyone has tried this, please let me know. If not ... I'll post the
> results.
> - Keman
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