Bosch O2 sensor

Discussion in 'Z32 Technical' started by ewschinzel, Mar 18, 2019.

  1. ewschinzel

    ewschinzel Member

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    The Bosch O2 sensors have 3 wires, two whites and one black in the centre.
    The original O2 harness colours are black, white in the centre and black/red
    Question:
    Do they New O2 plug straight in the original connectors or do the wires have to changed around?
    The wiring diagram says the white coloured one from the original O2 goes to the ECU pin 29 and 55 ..Signal wire and engine ground?
    Black/red is voltage supply connects to a fuse in the relay box
    Black is ground ECU pin 115

    So I guess the black wire on the Bosch is the signal wire to the ECU? pin 29/55?
    The two white wires must be the heating wires..is that right?

    Anybody can enlighten me on this one?

    Thanks
     
  2. zx299

    zx299 Well-Known Member

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    You are overthinking things

    The Bosch O2 sensors I have for sale were manufactured for the zed. Plug in and drive away :cool:

    FYI, yes you are correct ...... the black is signal and the two whites are heater
     
  3. tjleilo

    tjleilo New Member

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    Hi! I have a question related to this too. On my driver side oxygen sensor plug, (the plug on the engine wiring harness to the ecu) my black wire broke off, and I’m assuming it’s been causing me some performance issues. I bought a replacement coil pack connector/o2 sensor replacement plug but all of the wires are black. They are no longer white, red and black, and black. Is there any way to easily know which wires I must solder together? And what does that black wire do? Could it have caused performance issues?
     
  4. rob260

    rob260 Moderator Staff Member

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    Those patch harness type connectors are not the best for o2 sensors as the signal wire is shielded. You are going to end up with a sector of un shielded wire where you splice the new connector in.

    A better option is to crimp new pins on to the existing harness side wire. I have plug and pin kits in stock if you need and cheap. PM if interested.
     
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  5. zx299

    zx299 Well-Known Member

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    The broken wire on your harness goes to a heater wire on the O2 sensor

    An O2 sensor does not function until it reaches a very high temperature ...... the heater is there to make sure the sensor gets to operating temp as quick as possible. Not having the heater means your O2 will NOT be working for the first few minutes (until the exhaust gases heat up the O2)

    When fitting the new harness you bought, be sure to solder the centre wire to the WHITE wire on the engine harness. The wires in your original harness will probably be pretty cruddy, so cut them back the length of your new harness in order to find some decent copper to solder. Try and preserve the shield wire if possible, but it's not critical (none of the wires on the O2 sensor are shielded)

    If you aren't proficient at soldering, I would suggest getting someone else to do it for you :cool:
     
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  6. tjleilo

    tjleilo New Member

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    I would solder the new wires and plug onto the existing harness wires and then use heat shrink after I finished soldering. Would there still be an issue? Thank you for your reply by the way!
    I already bought the new plug so I’m going to try that first but I’ll keep your offer in mind, thank you!
    Would it still be an issue if I soldered then on and used heat shrink as stated above?
     
  7. tjleilo

    tjleilo New Member

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    Awesome! Thank you for your reply! Great information! What do you mean by shielded wire? I bought the Bosch O2 sensor and have had those installed for a while and it came with the plug as well. My harness wires are the red/black, white, and black wires that are all shielded and the new wire/plug kit that I have, all have shielded wires as well (only difference is that the shield color is all black, so that can cause confusion) sorry for my confusion. But what do you mean none of the O2 sensor wires are shielded?
    Every wire I see has that color shield around it.
     
  8. zx299

    zx299 Well-Known Member

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    There's a bare wire braid in your engine harness that acts as an electromagnetic signal shield .... you'll see it when you start stripping back the harness to fit your new connector. Try to preserve it, but it's not the end of the world if you don't ... the O2 sensor leads are 60cms long and they aren't shielded

    What you're referring to is the pvc wire insulation
     
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  9. tjleilo

    tjleilo New Member

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    Oh! Makes sense. Thank you so much for your replies! I can’t thank you enough! I hope you have a great day!
     
  10. tjleilo

    tjleilo New Member

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    I apologize, I actually have one last question. Would there be any problems with me just cutting off the wires where they go into the existing plug and then just cutting off that insulation and soldering the new plug to that? It makes it a lot easier so that I don’t have to tear into the harness. Could that cause any issues?
     
  11. zx299

    zx299 Well-Known Member

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    The only reason I say to cut the harness back a few extra inches is to get to some reasonably clean copper. The zeds are 25-30 yrs old now and the ends of the harness tend to be badly oxidised, and green copper is not conducive to good soldering

    If you're going to fix something on your zed, do yourself a favour and spend an extra 5-10 minutes doing the job properly (the first time) ... it will pay huge dividends for you later on

    If you want to enjoy a reliable zed (and who doesn't) you have to start doing some 'preventative maintenance'. That means when you come across something a bit dodgy (like a broken O2 sensor wire :rolleyes:) you fix it now rather than wait till it sh@ts itself and leaves you stranded in the middle of nowhere :cool:
     
  12. tjleilo

    tjleilo New Member

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    Makes sense and agreed. I bought my Z just over a year ago and have done TONS of work on it since repair shops do shotty jobs and I have to go back and fix what they did. No one spends the time to do it right, I definitely hear ya there. Will do with cutting back the harness. Thank you so much for your help, and I’ll definitely do all I can to keep another classic on the streets!
     

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