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Wire question....


adsm08

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So since the wire isnt carrying voltage, the ECM thinks the motors lean...therefore dumping tons of fuel to compensate, therefore causing rusty the person a PITA. Correct?
Almost.

That wire is a ground, so it should never have voltage. The voltage should drop across the load, which in this case would be the computer's circuit for monitoring O2 sensor voltage. But it is still needed to see the voltage.

Think of it like a hotwater-radiant heat system. You have a water pipe with a pressure gauge (voltage is electrical pressure). A pipe is burst after the gauge, but the last shutoff valve is before the gauge. You have pressure, you know it's there, but since it can't pass through the gauge without a way to return to the other side of the system, you can't see that pressure.

The hot side is your pipe to the shutoff valve. The voltmeter is the pressure gauge, and the burst pipe is your ground that isn't working.


So the hot wire is carrying the voltage, the ground is malfunctioning, and so the computer can't see the voltage, causing Rusty the computer a PITA when none of the things it does to make the O2s react do anything, making it run stupid, causing Rusty the person a PITA.


I have gone through the exact symptoms you have described in chasing this twice in my life. Both times it took me way too long to find the problem.

The first time I found my oxygen sensor broken in two. The second time that ground got damaged during an engine replacement.
 


rusty ol ranger

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Almost.

That wire is a ground, so it should never have voltage. The voltage should drop across the load, which in this case would be the computer's circuit for monitoring O2 sensor voltage. But it is still needed to see the voltage.

Think of it like a hotwater-radiant heat system. You have a water pipe with a pressure gauge (voltage is electrical pressure). A pipe is burst after the gauge, but the last shutoff valve is before the gauge. You have pressure, you know it's there, but since it can't pass through the gauge without a way to return to the other side of the system, you can't see that pressure.

The hot side is your pipe to the shutoff valve. The voltmeter is the pressure gauge, and the burst pipe is your ground that isn't working.


So the hot wire is carrying the voltage, the ground is malfunctioning, and so the computer can't see the voltage, causing Rusty the computer a PITA when none of the things it does to make the O2s react do anything, making it run stupid, causing Rusty the person a PITA.


I have gone through the exact symptoms you have described in chasing this twice in my life. Both times it took me way too long to find the problem.

The first time I found my oxygen sensor broken in two. The second time that ground got damaged during an engine replacement.
Ok, i think i understand now. Thanks for the paitence. Electrical stuff has never, ever been my strong suit. I cant even wire a trailer and make it work right half the time.

So, that being said, whats the best way to fix the wire to prevent this again? Should i cut out that section, splice it (what kinda splicer you reccommend?) Or do you think a taper up and go would suffice?

Im thinking im just gonna mend the wire, toss the intake back on and give it a shot. Not like pulling the upper intake was hard.
 

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My understanding of a three wire O2 sensor is a little different. You have a signal wire... a heater power wire... and a heater ground wire. The ground wire is dedicated to the O2 heating element. If you lose ground... you lose the heater and the O2 has trouble staying hot and reporting to the ECM. There are 2 wire and 4 wire O2 sensors that have a signal ground... but I believe this 3 wire O2 does not use a signal ground.
 

adsm08

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Ok, i think i understand now. Thanks for the paitence. Electrical stuff has never, ever been my strong suit. I cant even wire a trailer and make it work right half the time.

So, that being said, whats the best way to fix the wire to prevent this again? Should i cut out that section, splice it (what kinda splicer you reccommend?) Or do you think a taper up and go would suffice?

Im thinking im just gonna mend the wire, toss the intake back on and give it a shot. Not like pulling the upper intake was hard.
I have noticed that electrical and you don't get along. I think a lot of people have problems with it because you can't see the electricity moving. That's why I like the plumbing analogies, most people understand plumbing well, at least how it works, and really plumbing and DC electricity aren't that different.

I would cut out the frayed section and splice in a new piece, and then get it back int the loom. Then wrap it up with this stuff, rather than electrical tape:
https://www.ebay.com/i/221871365736?chn=ps

Ideally the new section would be soldered in, but that may not be a viable option, if there isn't enough space. If I can't solder on something I don't like using the pre-plasticed butt crimp you but at the parts store. I prefer to get the bare ones, like these:

https://www.amazon.com/s/?ie=UTF8&keywords=uninsulated+wire+terminals&tag=googhydr-20&index=aps&hvadid=176321532379&hvpos=1t1&hvnetw=g&hvrand=17411771137575935164&hvpone=&hvptwo=&hvqmt=b&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9006593&hvtargid=kwd-51852978845&ref=pd_sl_80vciyfjs1_b

And use them with heat shrink tubing. Always use GOOD heat shrink (gotta have the glue in it) and steaked crimps under the hood.

I will only buy heat shrink tube at Napa. It's like $15 for a bag, and in the summer I usually go through two bags a month, but I do a lot of wiring.

You are absolutely right about that intake though, it's one of the easiest to get off on an EFI engine. I'd fix the wire, throw the intake back on, and take it for a spin, see what happens.


My understanding of a three wire O2 sensor is a little different. You have a signal wire... a heater power wire... and a heater ground wire. The ground wire is dedicated to the O2 heating element. If you lose ground... you lose the heater and the O2 has trouble staying hot and reporting to the ECM. There are 2 wire and 4 wire O2 sensors that have a signal ground... but I believe this 3 wire O2 does not use a signal ground.
Your understanding is almost mostly correct.

Any electrical circuit, even one for just monitoring voltage, needs a ground. You understanding of the heater circuit, it's ground, and a 4 wire sensor are all spot on.

In a 4 wire oxygen sensor the signal an signal ground both run from the sensor to the computer. This gives a cleaner signal and allows for a little more sensitivity in the responses.

In the 3-wire system the signal + goes from the sensor to the computer, and then a totally separate ground goes from the computer to ground, usually on the engine somewhere.

When you hook up a voltmeter to test voltage on a wire you still have to ground on lead or you get a reading of zero. The circuit used to monitor the 02 sensor is just a voltmeter, it still needs that ground or it reads zero.
 

Uncle Gump

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Sorry adsm...

I had to go back a read your previous posts to find exactly what you were saying... post 14 is where you say that the orange wire is a ground wire the ecm uses for low reference of the O2 signal circuit... I missed that.

So to sum it up... 3 wire O2 sensor... One wire for the signal... one switched battery wire for the heater... One ground wire for the heater. That heater ground has nothing to do with the O2 signal circuit... The orange wire in question is the ecm's dedicated low reference circuit that the ecm uses to reference O2 signal circuit to.

Edit: When I said that the heater ground circuit has nothing to do with the O2 sensors signal circuit... that is a somewhat a false statement. Technically... it has a lot to do with the O2 sensors signal. The O2 sensor heater is there to get the O2 sensor hot quicker and keep it there so the O2 sensor functions. If it isn't hot... it doesn't work.

adsm... I think we were both on the same page... I think I got lost lost somewhere between the heater pipe... and the shut off valve... lmao

Rusty... hang in there buddy. I think you get yourself to worked up making the electrical and electronic engine controls a bigger hurdle then they need to be. Take a deep breath...
 
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rusty ol ranger

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Rusty... hang in there buddy. I think you get yourself to worked up making the electrical and electronic engine controls a bigger hurdle then they need to be. Take a deep breath...
Im tryin lol. Ive spent many hours learning the ins and outs of carburators thru my youth. Now ill have to spend many MANY hours learning EFI.

Either way, got the wire mended, it was almost spilt right in two pieces. Ran outta time before i could put the rest back togther. But the other wires in that general area look good. Keeping my fingers crossed.
 

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Dang Rusty... I thought maybe you had just set fire to 2.0.

If that wire was nearly in two pieces... It could very well be the smoking gun here. At a minimum it had high resistance and would completely suck as the low reference point for the ECM to compare a 1 volt or less signal circuit to. It would be worth checking continuity to ground from the ECM connector for that circuit... just to ensure that your repair is good. If it is good... check it off the list... and go for a drive... if the problem still exists... at least you will know what the problem isn't.

Good luck...
 

rusty ol ranger

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Nah. Only vehicles of mine that go up in flames are involuntary....lol.

When i found the wire it was laying up against the intake manifold/valve cover and bare as a baby ass. Im sure there wasnt any voltage going thru it. Plus i was getting a lean O2 code.
 

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Well... we need to be clear here... There should never be any voltage on that wire. It is a dedicated low reference (ground) for the ECM to compare the O2 sensors signal circuit to.
 

rusty ol ranger

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Well... we need to be clear here... There should never be any voltage on that wire. It is a dedicated low reference (ground) for the ECM to compare the O2 sensors signal circuit to.
By voltage i meant current of any kind. It wasnt doing its job woulda been a better statement lol
 

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