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3 wire O2 installation


sfR87quest
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  • 3 weeks later...
  • 9 months later...

O.K so this means that if you have a car with an AF guage we have to run the black wire to the gauge only or we splice it in half and run one to the gauge and then one to the ECU?                                                        

3 wire O2:

 

2 white wires

1 black wire

 

1 white to 12V positive

1 white to negative ground

black to gauge unit/ECU

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  • 2 weeks later...
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I have a question the WHITE wire that goes to 12v positive, can that be connected directly to battery?  Or does the 12v need to be switched, and if it needs to be switched, where is a good tie in for it?  I am adding a 3 wire on Saturday and just want to get it right the first time, Thanks guys and gals for all the info you all have been a lifesaver a time or two!
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...can that be connected directly to battery?  Or does the 12v need to be switched, and if it needs to be switched...

Most of us use switched power - it's available at the wiper motor electrical connection...

 

Mike

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  • 2 weeks later...
Most of us use switched power - it's available at the wiper motor electrical connection...

 

Mike

 

Would you be able to pinpoint what color code wire it is from the wiper motor ? My car is not running right now and it would be impossible to get a reading coz my battery is shot.

 

Thanks,

Joe

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  • 2 weeks later...

Heated O2 sensors (3 and 4 wire types) start working more quickly and they're more consistent in their readings... O2 sensor output voltage, for a given air/fuel ratio, is also affected by exhaust temp.  With a heated sensor this temp sensitivity is reduced.

 

The extra wire in 4-wire O2 sensors is a sensor ground.  Rather than using the sensor body for ground - and thus having to go through the exhaust manifold, engine block, etc. to get to the true chassis ground and then to the ECU, 4-wire sensors have a dedicated wire for the ground... just run this straight to the ECU along with the regular signal wire.  Now the O2 signal is independent of any poor/noisy engine grounds.  The ECU has a more reliable signal to work with.

 

4-wire O2 sensors need not be wideband; in fact most are not wideband.  Wideband sensors have several wires because they have several bits inside them that must be read/controlled properly to get a true reading... thus the expensive electronic controllers for wideband controllers.

 

mike c.

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  • 9 months later...
I found that most cars that come with a 3 wire HO2S have a resistor across the positive and negative for the heating element (to redirect unused power after sensor is up to proper heat). There is no mention of this in the post and the sensor life might be reduced with a constant 12 volt signal to it (especially when it is not needed).

 

Here is a link on how to wire it correctly:

http://www.plxdevices.com/AppNotes/PLXApp004.pdf

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