Oxygen sensor voltage?

giddyup306 · Dec 12, 2004

leakyfaucet said:
Hmm. So I shouldn't even try this without that? I guess you can get this at a Chevy dealer?

Also, I was looking at this test:
http://www.veryuseful.com/mustang/tech/engine/images/o2SensorTests.gif
And it appears to be for a newer mustang, I think. My connectors only have 3 prongs. What should I do?

Are you sure you can't backprobe the harness? That's what I'd do.

leakyfaucet · Dec 12, 2004

Do you mean force the lead into the same hole that the wire goes into on the female connector? Sorry, I'm not good with electrical terminology.

giddyup306 · Dec 12, 2004

leakyfaucet said:
Do you mean force the lead into the same hole that the wire goes into on the female connector? Sorry, I'm not good with electrical terminology.

Yep. Just make sure your lead touches the connector inside the harness. If it is too big you can get extensions that are smaller diameter and will fit.

leakyfaucet · Dec 12, 2004

Okay, I'll see if that works. Give me a minute.

leakyfaucet · Dec 12, 2004

Alright. I taped a sewing needle to my prong because I needed something tiny to penetrate with. I couldn't figure out which ones were the sensor wires. The closest I could see to a dark green or dark blue with pink was a dark green with a purple stripe wire. I tapped it and grounded it using the computer ground. I got a constant signal of around 2V but only with the negative prong grounded. When I grounded it, the car sounded differently, like it was running extra rich or something. When I pulled the negative prong off, the car ran like normal again.

Thoughts?

HISSIN50 · Dec 12, 2004

is testing being done at the puter wiring harness or at the sensor?

giddyup306 · Dec 12, 2004

I think he's gonna do it at the harness.

leakyfaucet · Dec 12, 2004

Yeah, I did it at the computer harness.

Oh yeah, and the voltage stayed even with the engine off, with the key on. So obviously I didn't get the right wire. Any one know for sure which wires to tap?

jrichker · Dec 12, 2004

leakyfaucet said:
Yeah, I did it at the computer harness.

Oh yeah, and the voltage stayed even with the engine off, with the key on. So obviously I didn't get the right wire. Any one know for sure which wires to tap?

See http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model cars

See http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model cars

See http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model cars.

I usually use a safety pin to backprobe the wiring connectors.

giddyup306 · Dec 12, 2004

nevermind

HISSIN50 · Dec 12, 2004

leakyfaucet said:
Yeah, I did it at the computer harness.

Oh yeah, and the voltage stayed even with the engine off, with the key on. So obviously I didn't get the right wire. Any one know for sure which wires to tap?

i think Joe told you which pins to use, in his post on page on.

good luck.

P.S. thanks for the clarification - you two had a nice banter going and i missed where the probing was going on.

leakyfaucet · Dec 12, 2004

Every single diagram I've seen including my Haynes manual shows completely different wire colors. The autozone diagram that jrichker supplied (thanks) said Red with black and the other being Grey with light Blue. I'm going to look for those.

I'll tell you how it goes.

leakyfaucet · Dec 12, 2004

I'm pretty sure the autozone diagram was correct. I looked at my o2 sensor harness and it also had the same gray with light blue wire as well as the red with black wire. I tapped the grey wire at the computer and got absolutely no voltage even after running the car for a few minutes. Between that wire and the computer ground, I got a resistance of about 30 ohms, if that means anything to you electrical wizards.

I didn't check the other wire, due to the time it takes to get everything set up, but I'm sure it's the same way, and I get the codes for both of them failing.

Where should I tap next to track down the gremlin?

HISSIN50 · Dec 12, 2004

i can't read.

EDIT: i misread the ohms value the first time around. my bad. nevermind.

leakyfaucet · Dec 12, 2004

That's okay. So what would you do next if you were me? I think that if I keep pretending to be you mustang gurus, I'll get this done faster. =)

HISSIN50 · Dec 12, 2004

I'm still retarded. carry on.

HISSIN50 · Dec 12, 2004

im retarded. nevermind.

leakyfaucet · Dec 12, 2004

Is what I did how you test the quality of the ground? BTW about a month ago I cleaned up the ground and covered in vasoline. I used way too much, but I figured it wouldn't hurt the ground.

The ohms was the only reading I could get since I got no voltage, so I figured I'd tell you guys and see if you could figure it out. So should I test a the oxygen sensor directly? I guess I should tape a wire to the negative prong of the meter and put that on an engine ground or something?

HISSIN50 · Dec 13, 2004

leakyfaucet said:
Is what I did how you test the quality of the ground? BTW about a month ago I cleaned up the ground and covered in vasoline. I used way too much, but I figured it wouldn't hurt the ground.

The ohms was the only reading I could get since I got no voltage, so I figured I'd tell you guys and see if you could figure it out. So should I test a the oxygen sensor directly? I guess I should tape a wire to the negative prong of the meter and put that on an engine ground or something?

man, im having a bad night. i need to learn now to read. i thought you tested the resistance of the EGO ground to the puter ground (to check if the ground was alright). i have no idea what resistance should exist between the EGO wires. im gonna go edit my above post so it makes sense and is not misleading to others reading this thread and future searchers.

at this point, im not sure which wires you are testing or what is going on - i wont post on this thread anymore.

i will add: did you put vaseline between the ground's connector and the surface it grounds too? i think the vaseline would be an insulator and not conduct too well. i would leave it clean or if absolutely necessary, use some conductive never-seize type product. i really would leave it clean though. again, i have no idea how you used the product, and with the night im having, i probably misread that too. LOL.

ok, leaving you alone now.

leakyfaucet · Dec 13, 2004

HISSIN50 said:
at this point, im not sure which wires you are testing or what is going on - i wont post on this thread anymore.

Ahh! No! You're the best chance I've got! Okay, the last thing I did was put the positive prong on my voltmeter into the back side of the left oxygen sensor wire going directly into the female end of the main harness that plugs into the computer (basically I tapped directly into what the computer would see), and I put the left prong from the voltmeter on the ground right next to the computer.

That make sense? That's all I did. While I was there, since I got no voltage, I flipped the switch to display resistance, and got 30 ohms.

So now that you're back with me, should I test the oxygen sensor directly? Would that even work?

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