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Discussion Starter #1
So I tried to start up my car after an overhaul, and I think that the 02 sensor wires got messed up through confusion of wiring diagrams.

gong back to the basics and using the diagram at the following links:

Diagram 1
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

and

Diagram 2
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

I think my Blk/LtGreen noted as power ground in diagram 1 or EEC pin 40 constant voltage in diagram 2 got swapped with the actual EEC signal wires at each O2 sensor connector feeding the actual O2 sensor.

So this would mean that the output of the sensor that is supposed to be going to to constant voltage for the EEC is actually going to the signal return of the EEC. IF this is correct this would lead to the car running extremely lean and not wanting to run. Correct.

Can I just swap these wires back and be all good, or have I done something irreversible that I am not thinking about?
 

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Discussion Starter #2
this has been a frustrating quest.
Does anybody have a diagram of the wires coming out of the O2 sensor? I can't seem to find one and plan on calling Bosch tomorrow, but thought I would ask here in the meantime.

Once I know how the wires are coming out of the actual O2 sensor, I can back track and check continuity on my wires from there.
Or, if you have a running 89-93 fox, perhaps you can go look for me.

This is what I am talking about: the diagram is from the veryuseful website on fox wiring, the other pics are of my connector on the harness. They don't match as I would expect that the diagram is supposed to be showing how the wires enter the harness side connector.



Thanks
 

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as helpful and the very diagram, and EVTM, is much better

has pin outs.

the pinouts changed

you need to be more specific in the year.

It would much better to trace it from the ecm to the sensor, and pin it properly and double check.

the only way to check for damage is to see if the ecm sees it in a data stream

using a tuning device like a tweecer.
 

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Discussion Starter #4
Thanks
Year is 1989.

I have no issue Travis g back to the ECM as that is what I will do, but I still need to know the wire order on the actual O2 sensor.

Any diagram on the O2 sensor itself?
I plan on calling Bosch tomorrow to verify.
 

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Thanks
Year is 1989.

I have no issue Travis g back to the ECM as that is what I will do, but I still need to know the wire order on the actual O2 sensor.

Any diagram on the O2 sensor itself?
I plan on calling Bosch tomorrow to verify.
that is the easy part

the two wires that are the same COLOR....white or black or blue.....are the heater circuit

the other two are the signal and signal ground

just hit the sensor tip with a butane or propane torch.......while the two non heater wires are attached to a millivolt scale and measure it.

the polarity will show up on the meter.

all 02 sensors follow this.
 

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Even not knowing above,

an ohm reading would have IDed the heater wires, and left you the sig and ground.
 

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Discussion Starter #7
Alright

My O2s have 2 larger gauge white wires and one smaller gauge black wire.

I will assume that the smaller black wire is the signal return to EEC.
 

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ohm the white to confirm what I said.
 

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Discussion Starter #10
My signal return wires are wired correctly to the O2 sensors then.

The power/ground shouldn't matter on O2 sensor side orientation, correct?
 

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My signal return wires are wired correctly to the O2 sensors then.

The power/ground shouldn't matter on O2 sensor side orientation, correct?
sensor and heater are TWO different circuits.

call them heater and sensor circuits.

heater circuit is NOT polarity sensitive, its a resistive heater.
 
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