MP4.2+6.0

I know exactly what these connectors are. I posted on them for the W12 repair, when you need to do the car side of the wiring harness and connector for O2 sensors. For a straight sensor replace, this is kind of yesteryear mid 80s stuff to me (for me, the 1985 Audi 5000S). For modern Bosch, if you just get the correct five digit part number, you then have the correct sensor, correct wire length and correct connector color for $80 to 100, instead of $200+ via dealer.

Yes, you can start down the road of concluding the wideband sensors are essentially generic, and assume your connector or nearby conductors is not actually the issue. Since you will be splicing that is--that is a big assumption BTW and contradicted by W12 experience and fragility of the signal (non power) individual conductors in the overall O2 wire set. Then you can proceed to do the solder in repair (takes two people realistically--BTDT with those specific Tyco connectors), and then either dynamite the wiring harness tape with plastic electrical tape that will fall off in a year, or do it right with the Audi cloth tape that will cost you another tens of dollars.

Net, notice some "***-u-m-ptions" in here and essentially the (non-)economics if you just get the right Bosch sensor by 5 digit #, let alone risk of a connector (or proximity) related failure. There is a time for those Tyco type connectors and I have used them quite successfully on 02 W12 work specifically on the car harness and connector side where you have no other option anyway realistically. Plus, I have used generic 02's back in yesteryear before full plug compatible ones were offered by Bosch. (The old ones were also either simple two wire, or 3 wire heated, and way before the internal electric feedback check systems that often drive the errors/codes now). But in my practical judgment and experience, this is not the scenario really, unless and until following a sensor replace you still have a conductor related O2 error and then conclude it is on the car side of the final connector that comes with the sensor. That is the W12 specific issue for example, and documented in a W12 specific TSB. But here it should be much simpler--plug and play replace a simple O2 at the connector and move on. Use the Bosch one OES at +/- $80-100, or Audi one at 2 1/2x that.

aTOMic

Got it. Wilco. Good to know that the wire length and connectors are exactly the same; that was my main concern, given the number of connector- and wire-related problems on this vintage Audis as evidenced by all the posts about pin, connector, and wire related fault codes, especially in the harsh environment + necessary signal accuracy lambda sensor department. Thanks.

Audi cloth tape... must buy immediately. Probably won't ever need it. The story of my (garage) life.

"***-u-m-ptions". Yes, I see you attended university!

Alexxelax

Do anyone know wich one the oxygen sensor B4S1 is?

MP4.2+6.0

B4 S1 means the forward sensors (S1) before the main converters. Bank 4 is the rear of the motor on the right side when you look under the hood--U.S. or Continental Europe driver's side. I'll leave you to figure out which sensor in turn is in the diagram for that rear part of the motor--on an S8 I think the down pipes do some up and down bends like headers so the diagram is confusing. PaulW (more frequent on QuattroWorld than here) and one other poster or two) have dealt with the O2's on an S8. W12 ones turn out to be a lot easier to reach apparently.

Alexxelax

Thanks, so senor 4 before cat IV

EricVonHa

Correct

carl viking

MP, are you sure? I "heard" that actually there are two sensors on the W12 that are impossible to swap without dropping engine. The two post cat, most forward ones. B1S2 and B2S2, right?

These two - in red:




I have this recurring nightmare of that happening.... Again....

MP4.2+6.0

Post cat ones, yes nightmare on W12, but not pre cat ones. The pre cat ones (four total) are screwed into the exhaust manifolds (broken into three cylinders each) and with the right technique can be done under hood with a simple crows foot wrench. Did it myself, both the forward and rearward manifold locations. Way easier than my C5 4.2 where I literally had to climb on top of the motor crouched under the hood and reach down blind to get at those sensors. If you look at the S8 diagram below, apparently the forward sensors (the S1 type) are still back behind the motor instead of to the sides like the W12. That's the difference from pretty easy, to at least pain in butt like my C5 was, and sometimes worse.

Fortunately, pre cat ones are the ones that usually fail (if they do) rather than post cat. The post cat ones don't have the heating element either so are simpler in design.