O2 Oxygen Sensor multimeter test

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shawski

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O2 Oxygen Sensor multimeter test-VIDEO

Hi all,
My truck has been running rich since I bought it. The engine needed rebuild immediately due to blown gasket somewhere after 330k miles. I replaced a few of the accessory components along with the engine.
I believe my truck is running rich even after warm-up. So I decided to start with testing the O2 sensor.
I believe the results I received are not good. Here's a link to my 55 second video of the test while in the engine. Can someone give me their "professional" opinion?
https://youtu.be/3TQSkBG0vP4

Thanks in advance!
Shaw
 
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I don't know what the values should be, but it seems to be showing fuel on when you're revving the engine up, and fuel off when you let off the throttle, so its seeing what it should. Whether the values are correct or not, I dunno. What manual are you using to determine the proper values?

And what leads you to believe its running rich? Are the plugs wet? I posted a link to reading spark plugs somewhere on here, but it would just be easier to google it.

If it is running rich, and you believe its the o2 sensor, they're relatively cheap to replace. I'd suggest buying NTK brand's o2 sensor, its 25 bucks from RockAuto. I have a brand new (used maybe 15 miles or so?) Denso that has checked out to be bad, so I wouldn't recommend buying a Denso o2 sensor.

If after you replace the o2 sensor and its still running rich, check to see if someone's opened the MAF sensor and played with the gear inside. You can turn it down if it is running rich, but be careful as you can go too lean and blow that engine quite easily.
 
flyinhawaiian01 said:
I don't know what the values should be, but it seems to be showing fuel on when you're revving the engine up, and fuel off when you let off the throttle, so its seeing what it should. Whether the values are correct or not, I dunno. What manual are you using to determine the proper values?

And what leads you to believe its running rich? Are the plugs wet? I posted a link to reading spark plugs somewhere on here, but it would just be easier to google it.

If it is running rich, and you believe its the o2 sensor, they're relatively cheap to replace. I'd suggest buying NTK brand's o2 sensor, its 25 bucks from RockAuto. I have a brand new (used maybe 15 miles or so?) Denso that has checked out to be bad, so I wouldn't recommend buying a Denso o2 sensor.

If after you replace the o2 sensor and its still running rich, check to see if someone's opened the MAF sensor and played with the gear inside. You can turn it down if it is running rich, but be careful as you can go too lean and blow that engine quite easily.
Click to expand...

Thanks Flyin Hawaiian. I always appreciate your commentary on this forum. The only sign I have that it's rich is the continued strong odor of gas from the tailpipe after warmed up. I cannot drive with the rear window down or else the odor comes through very heavy, even through the side windows at a red light with the right breeze.
I have not checked the plugs yet, but thank you for that idea.
The MAF looks unmolested and seems to be functionally correct from my tests at engine rebuild 2500 miles ago.
I now have my FSM out and the O2 test says you need a SST which allows you to connect a meter to the engine diagnostic plug (essentially). I don't have that SST, so I may have to find one to rent or buy. The FSM has a nice chart to follow, "if this, then this", sort of thing.
I'll be in touch with an update.
In the mean time, anyone else have anything productive to contribute?
Thanks!
Shaw
 
Thanks for the kind words! I don't know a lot, but what I do, I try to share!!!

Hmmm, fake catalytic converter by chance? You'll usually get the rotten egg smell and not so much the raw fuel smell. Could be whoever had it before hollowed out the cat.

Are you required to pass smog where you're at? If so, and the cat was hollowed out, you definitely wouldn't pass, so I'm just wondering if this has been an issue yet.

As for the sst, its just the jumper for setting the timing. Just jump T and E1 with a wire or paper clip. Here's a complete start to finish test of the o2 sensor:

http://kolohe.net/t4r/o2%20sensor%20testing.pdf

At this point, I'd just go through and do all the main stuff. Reset the ecu (pull fuse method), then start with new plugs (unless you've changed them recently), regapped properly, set timing with jumper to 5ºBTDC, set idle at 750rpm, check TPS, warm up and check for codes, then do the test for the o2 sensor.

And, I'm assuming you're on a non-cali emissions engine, right? You only have 1 o2 sensor, correct?
 
flyinhawaiian01 said:
As for the sst, its just the jumper for setting the timing. Just jump T and E1 with a wire or paper clip. Here's a complete start to finish test of the o2 sensor:
Click to expand...

If I jump the T to the E1, how do I connect the red and black of the multimeter to one paperclip?
Can you elaborate?

Thank you!
 
Just follow the pdf file I sent ya, that should put you on the right track. You won't have T and E1 jumped while testing the o2 circuit, you will disconnect that, then measure the voltage between VF1 and E1. If its 0VDC, and you have no codes set, disconnect the pcv hose and check voltage again. If still 0VDC, replace o2 sensor.

If you get more than 0VDC, its something else that is going on and you'll need to check other settings. See where this test gets you first before exploring other issues.

You have the OEM manual for your vehicle? If not, search here, there's a bunch of threads with links to online OEM manuals.
 
flyinhawaiian01 said:
Just follow the pdf file I sent ya, that should put you on the right track. You won't have T and E1 jumped while testing the o2 circuit, you will disconnect that, then measure the voltage between VF1 and E1. If its 0VDC, and you have no codes set, disconnect the pcv hose and check voltage again. If still 0VDC, replace o2 sensor.

If you get more than 0VDC, its something else that is going on and you'll need to check other settings. See where this test gets you first before exploring other issues.

You have the OEM manual for your vehicle? If not, search here, there's a bunch of threads with links to online OEM manuals.
Click to expand...

Thank you. I have the 1985 4runner FSM, I couldn't find a digital copy for my '87.
I will follow the PDF and see where I get. I may have more questions, if you don't mind.
 
flyinhawaiian01 said:
Just follow the pdf file I sent ya, that should put you on the right track. You won't have T and E1 jumped while testing the o2 circuit, you will disconnect that, then measure the voltage between VF1 and E1. If its 0VDC, and you have no codes set, disconnect the pcv hose and check voltage again. If still 0VDC, replace o2 sensor.

If you get more than 0VDC, its something else that is going on and you'll need to check other settings. See where this test gets you first before exploring other issues.

You have the OEM manual for your vehicle? If not, search here, there's a bunch of threads with links to online OEM manuals.
Click to expand...

I'll follow the PDF to a T, thanks. However, regarding the analog multimeter, am I connecting the red side to the 1 wire on the O2 sensor and the black to the main battery ground?
 
Yep, that'll get you the correct reading. If its not quite right, try a wire brush on the housing of the o2 sensor so you get a good ground.
 
Failure on the testing tonight. I couldn't get the analog meter to feedback anything. I put the dial on 50V setting. I tested the car battery to make sure the meter has power and was operable, got 12-14V reading on battery...so that works.
I put a red alligator clip on the prong of the single O2 wire, then clipped that to the red side of the multimeter (the female plug on the wire harness was left not connected). The black probe went to the battery ground. Had the RPM's at 2500 and there was zero movement on the meter. I was expecting to count the meter go back and forth multiple times for 10 seconds and I didn't get that opportunity.
Side thought, when I connect a digital multi meter i get readings as the RPM's rise and lower.
Thanks for your input!
 
Yeah, that's not gonna work actually. Its early this morning, so maybe I'm not thinking this through, but that sensor should only be reading tenths of volts, as shown in your video with the Fluke meter (unless you have it set in a different range). Your video is showing POINT 6 volts, not 6 VOLTS.

And if I'm not mistaken, this test should show you 0 volts anyways to test correctly. If you see anything other than 0 volts between VF1 and E1 at the diagnostics connector next to your fuse block under the hood, you need to replace the o2 sensor.

Have you done the resistance check on the o2 sensor yet? That's the easiest way to determine whether its bad or not.
 
I need to bring this back to life. I tried some testing and ultimately gave up, for the $45 to replace with new, I've now got a new one from my buddies at 22reperformance.

On the last O2 sensor, which came with the truck when I bought it, I didn't throw any check engine signals. I've been using that sensor for approx 3k miles on the new rebuilt motor. With the new sensor in, I throw code 5.

Is it possible I confused the computer because, poof, I have a new sensor? I did disconnect the ground at battery upon install. Is there anything else I was supposed to do at replacement?

OR, is the computer just now working the way it was supposed to with a good sensor in it?

thoughts and recommended next steps from you more experienced 22re guys, appreciated...
 
Okay, have some questions about your rig...

What year is this?
Is it single wire o2, or multi wire o2?
Is the exhaust stock, or is this on an aftermarket header?
If aftermarket, how far away is the o2 sensor from the exhaust ports?
Is the wiring in any way damaged in this vehicle?
Have you checked the ground to the engine block?
Have you completed a full tune up and set everything to stock settings? Ie., timing, idle, TPS, MAF gear, etc.
How long does it take for the code to come up? is it instant or only under load?
Still need to check the plugs to see what they look like. That will tell you how the engine is running and whether its actually seeing a rich condition or if something seems to be askew.

Need to get the rig set up for a baseline before you go any further. Once everything's been set correctly, then you can start diagnosing the code. If any of those things are off, you'll never get to the root of the problem!

Shouldn't take too long to go through that list, a weekend's worth of work there and you should probably figure out exactly what the problem is.
 
Thanks!
Answers:
1987
single wire
stock exhaust (and rest of the rig too)
NA
Haha, I haven't personally seen 100% of the truck wiring to say. What I have seen/repaired, is good working order. It's 30 years old and lived in the desert it's entire life...for what that's worth.
engine block ground is good since the rebuild.
Stock settings, per FSM, on timing, idle, TPS, MAF (assuming so since plug isn't drilled out), etc.
the engine light comes on solid for approx 3 minutes at a time, in 5-10 minute intervals. I haven't seen it come on until after the motor was warmed up.
I pulled the #1 plug last weekend, it looked optimal, no sign of richness.

I appreciate you taking the time on this. I think I may take the truck into a local toyota guy and have it tuned up and inspected. I've got the engine to 90%, maybe I should let a "pro" take it across the finish line.

Based on my answers, any additional thoughts?
 
Yeah, I've got nothin' now! All I can think of is that this new o2 sensor might be a bad one. Its not a Denso brand is it?

I literally have one of those that didn't work in my truck just a few months ago. Brand new from RockAuto, ended up failing smog. Another guy swapped it out with a new one from NTK, and it worked perfectly and actually passed once the bad ground on the engine was replaced! I didn't even have to lean it out with the MAF this time round!!!

If you do take it in to them, report back with what they found, I'd love to find out what actually is causing this issue! It would be good for future o2 sensor issues for other folks!!!
 
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