Help identifying O2 sensor connectors

Dr. Zed · Post by **Dr. Zed** » Tue Mar 05, 2024 2:42 pm

So I've come to replace the O2 sensors and I've watched some videos so went ahead and removed the two probes down by the left side of the engine as these are the pre cat sensors. I then followed them up and they double back on themselves to connect to just below the coil packs (purple in the image), but I thought these sensors travel along the back of the engine, and then up along the top to connect to the connectors beside the manifold (in red).

Anyone shed some light on this?
Obviously if the sensors run to there then that's all I can do to replace them. One of them definitely isnt long enough to the reach the parts in red regardless, but I'm so confused!

enuff_zed · Post by **enuff_zed** » Tue Mar 05, 2024 2:44 pm

Pretty sure the connectors are the first ones you found, below the coil packs where they double back and clip in.

Dr. Zed · Post by **Dr. Zed** » Tue Mar 05, 2024 2:55 pm

enuff_zed wrote: ↑Tue Mar 05, 2024 2:44 pm Pretty sure the connectors are the first ones you found, below the coil packs where they double back and clip in.

Thanks mate! The speed at which I can get help here is one reason why I love owning a z4

The video I watched was a different style Z4, the one with the grey/silver engine cover and had vastly different connectors so maybe it's just part of the update for that Zed.

Thanks mate, appreciate it!

enuff_zed · Post by **enuff_zed** » Tue Mar 05, 2024 3:03 pm

Dr. Zed wrote: ↑Tue Mar 05, 2024 2:55 pm
enuff_zed wrote: ↑Tue Mar 05, 2024 2:44 pm Pretty sure the connectors are the first ones you found, below the coil packs where they double back and clip in.
Thanks mate! The speed at which I can get help here is one reason why I love owning a z4

The video I watched was a different style Z4, the one with the grey/silver engine cover and had vastly different connectors so maybe it's just part of the update for that Zed.

Thanks mate, appreciate it!

That would have been an N52 engine.
You have the M54.

Dr. Zed · Post by **Dr. Zed** » Tue Mar 05, 2024 4:27 pm

enuff_zed wrote: ↑Tue Mar 05, 2024 3:03 pm That would have been an N52 engine.
You have the M54.

That'd make sense.
Well I've replaced them, what a pain that was. Engine started smoking for a few minutes down where I replaced them and then it went so dunno what that's about.

But it hasn't fixed the issue so...

Mike6 · Post by **Mike6** » Tue Mar 05, 2024 6:31 pm

Dont think you have mentioned what the problem is. Has a code been thrown in which case you will need a code reader to tell you what needs replacing. Could it be the post cat sensors that you need to replace.

enuff_zed · Post by **enuff_zed** » Tue Mar 05, 2024 6:42 pm

Mike6 wrote: ↑Tue Mar 05, 2024 6:31 pm Dont think you have mentioned what the problem is. Has a code been thrown in which case you will need a code reader to tell you what needs replacing. Could it be the post cat sensors that you need to replace.

Yeah, he did, but on a different thread.
viewtopic.php?p=2058452

Dr. Zed · Post by **Dr. Zed** » Wed Mar 06, 2024 5:53 pm

Mike6 wrote: ↑Tue Mar 05, 2024 6:31 pm Dont think you have mentioned what the problem is. Has a code been thrown in which case you will need a code reader to tell you what needs replacing. Could it be the post cat sensors that you need to replace.

Yeah, sorry. Was on a separate thread. This thread was just about trying to locate the correct connectors which then it spiralled!

Dr. Zed · Post by **Dr. Zed** » Wed Mar 06, 2024 5:55 pm

enuff_zed wrote: ↑Tue Mar 05, 2024 6:42 pm
Mike6 wrote: ↑Tue Mar 05, 2024 6:31 pm Dont think you have mentioned what the problem is. Has a code been thrown in which case you will need a code reader to tell you what needs replacing. Could it be the post cat sensors that you need to replace.
Yeah, he did, but on a different thread.
viewtopic.php?p=2058452

Well, brought the car to a garage. Reluctantly. Cash in hand, £60 because he just charged me for the diagnostics but was much cheaper than other places that wanted 120+.

All sorted though. He said there was a small crack in an air line that I missed but he just replaced it as he had a spare. And then he reset the codes with some decent kit (ie not Carly!), and all good now.

After all that. But glad it's done now.

enuff_zed · Post by **enuff_zed** » Wed Mar 06, 2024 6:00 pm

Dr. Zed wrote: ↑Wed Mar 06, 2024 5:55 pm
enuff_zed wrote: ↑Tue Mar 05, 2024 6:42 pm
Mike6 wrote: ↑Tue Mar 05, 2024 6:31 pm Dont think you have mentioned what the problem is. Has a code been thrown in which case you will need a code reader to tell you what needs replacing. Could it be the post cat sensors that you need to replace.
Yeah, he did, but on a different thread.
viewtopic.php?p=2058452
Well, brought the car to a garage. Reluctantly. Cash in hand, £60 because he just charged me for the diagnostics but was much cheaper than other places that wanted 120+.

All sorted though. He said there was a small crack in an air line that I missed but he just replaced it as he had a spare. And then he reset the codes with some decent kit (ie not Carly!), and all good now.

After all that. But glad it's done now.

Phew!!!

Dr. Zed · Post by **Dr. Zed** » Thu Mar 07, 2024 10:32 am

enuff_zed wrote: ↑Wed Mar 06, 2024 6:00 pm
Phew!!!

Yeah, so happy. He ran some health checks and all came back perfectly so they were legacy low voltage errors. He wasn't sure why the EML popped up if they were legacy but he said the O2 sensors might have needed to be replaced which triggered the EML, but when I replaced them it just didn't clear the EML because of all the other errors were wreaking havoc with the ECU.

Thanks for all the help as always mate!

BumpyZ4 · Post by **BumpyZ4** » Sun Mar 10, 2024 3:24 am

The connectors you have circled in red are for the post cat sensors.

Dr. Zed · Post by **Dr. Zed** » Sun Mar 10, 2024 7:56 am

BumpyZ4 wrote: ↑Sun Mar 10, 2024 3:24 am The connectors you have circled in red are for the post cat sensors.

Cheers mate! Got it all sorted. Thanks for the insight though.

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