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1990 Toyota Camry LE
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Discussion Starter #41
No, you cannot solder O2-sensor wire! Use crimp only because the sensor uses the air-gap between wire strands to sample outside air as reference signal.

The -0.1v at ECU shows a ground loop problem. Check all grounds
Well my ghetto O2 sensor actually has 2 parts where I have added wire so one is crimped and one is soldered LOL! So I technically still have one non soldered section.

As for the grounds im not sure where to look. The battery ground? There are 2 wires that go from the battery to chassis. There is this wire that's connected to alternator bracket and some other bracket near the cruise control, but I have no clue what it does. I do have a spoiler light that's grounded to the trunk.
When it comes to wires I probably have no clue where anything goes aside from what's plainly visible..
 

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85 camry 5spd dlx
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Wait, what?
Okay okay, so I did some reading....
@DanoXYZ are you on rennlist too? Lol



https://rennlist.com/forums/924-931-944-951-968-forum/989091-o2-sensor.html

A brief summary the O2 sensor used to have a hole in its body for reference air, it uses the strands of the wire to pull air now, so the controversy is the solder doesn't let air pass through. In my reading someone mentioned why not just put a hole in the insulation of The Wire. Also I'd say it's a 50-50 thing some people say if you solder away from the sensor it's okay. One person said it like I would think solder is always better than crimp connectors
 

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Porsche
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PorscheG96 is a buddy of mine. ;) I got paid to write some Porsche maintenance articles for Internet Brands. Don’t know exactly where they put it, might be on Pelican Parts. I’m actually Danno on Rennlist:
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/78698-do-not-solder-o2-sensor-wires-2.html

Depending upon O2-sensor design, they may put a hole on body of sensor to sample outside air, but these tend to be older, cheaper designs as it’s simpler. However hole causes easier contamination from water, dirt and mud. Hence the better designs uses reference air sampled between the wire strands.

Since this is very low-amperage signal with high-impedance interface, the wire conducts an extremely small signal. Something size of human hair is enough to send signal and most sensors use coaxially shielded cable to reduce interference. Stainless steel, chrome or nickle-plated wire is also used for longevity and reduced corrosion (since electrons actually flow on surface of wire, not through solid center).

What happens most of time with trying to solder stainless steel wire is you end up with incomplete penetration and the solder just sticks on top of wire. This leaves enough strands free on inside to sample outside air anyway. Since it’s such a small signal, as long as you connect a single strand across with solder, the signal will work. Just be sure to leave enough free-breathing strands for sampling outside air. Instructions at end of 1st page:

http://web.archive.org/web/20080719224017/apps.bosch.com.au/motorsport/downloads/sensors_oxygenlsm11.pdf
https://www.ericthecarguy.com/kunena/4-General-Automotive-Discussion/20744-soldering-o2-sensor-wires
https://grassrootsmotorsports.com/forum/grm/splice-o2-sensor-wire/65038/page1/l
http://www.alfabb.com/bb/forums/spider-105-115-series-1966-1994/151162-ahahaha-remember-solder-o2-sensor-story.html

Last link has 1st hand before & after comparison of soldered vs. crimped O2-sensor wire (shadowburn).
 

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What happens most of time with trying to solder stainless steel wire is you end up with incomplete penetration and the solder just sticks on top of wire.

I'm sorry, I've never had this problem. My boss is old school and he uses SS anywhere possible, nuts, bolts, connectors. Heck we've got a 2ft x 2.5ft x 1/4in plate of it at the shop (not the easiest to cut).

I will admit that when I first started using them, I had some troubles, it took me wasting 2 before I could do it
 

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Well my ghetto O2 sensor actually has 2 parts where I have added wire so one is crimped and one is soldered LOL! So I technically still have one non soldered section.

As for the grounds im not sure where to look. The battery ground? There are 2 wires that go from the battery to chassis. There is this wire that's connected to alternator bracket and some other bracket near the cruise control, but I have no clue what it does. I do have a spoiler light that's grounded to the trunk.
When it comes to wires I probably have no clue where anything goes aside from what's plainly visible..
Yeah there are multiple sensor signal-grounds (logic floating grounds) at ECU. They are all tied together somewhere and should have exact same potential as power/chassis ground. Measuring -0.1v shows that sensor/signal ground is not same as power/chassis ground and all your O2-sensor data will be skewed and incorrect (should be positive signal). ECU will make incorrect fuel-trim adjustments.

You can kinda test O2-sensor with multimeter but will be difficult to gauge the speed and peaks of sine-wave. You’ll want to see peaks of about 0.85v and lows of 0.10v with minimum 8-swings in 10-seconds. FSM says fewer swings than that should have O2-sensor replaced.

 

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Discussion Starter #48
Yeah there are multiple sensor signal-grounds (logic floating grounds) at ECU. They are all tied together somewhere and should have exact same potential as power/chassis ground. Measuring -0.1v shows that sensor/signal ground is not same as power/chassis ground and all your O2-sensor data will be skewed and incorrect (should be positive signal). ECU will make incorrect fuel-trim adjustments.

You can kinda test O2-sensor with multimeter but will be difficult to gauge the speed and peaks of sine-wave. You’ll want to see peaks of about 0.85v and lows of 0.10v with minimum 8-swings in 10-seconds. FSM says fewer swings than that should have O2-sensor replaced.

Hmm so is there somewhere specific I should be looking? Sorry, I am not very good with electrical wiring and it's logic. Would I be looking for a cluster of wires going from the harness to chassis? And would this be more on the ecu side inside the cabin or in the engine bay? Or are my guesses totally off base haha..

As for o2 sensor I actually replaced it about 2 weeks ago so I'd be fairly sad if it is the main problem.
Also never heard of the whole airgap in wires thing before so that was definitely interesting.
 

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Hmm so is there somewhere specific I should be looking? Sorry, I am not very good with electrical wiring and it's logic. Would I be looking for a cluster of wires going from the harness to chassis? And would this be more on the ecu side inside the cabin or in the engine bay? Or are my guesses totally off base haha..

As for o2 sensor I actually replaced it about 2 weeks ago so I'd be fairly sad if it is the main problem.
Also never heard of the whole airgap in wires thing before so that was definitely interesting.
FWIW I've been working on a bike at work. It's a mess, wouldn't charge ,even with fancy charging system installed (power dynamo).

So here is the before and after.



As for the ground, I'd check all grounds going to motor
 

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"Hmm so is there somewhere specific I should be looking? Sorry, I am not very good with electrical wiring and it's logic. Would I be looking for a cluster of wires going from the harness to chassis? And would this be more on the ecu side inside the cabin or in the engine bay? Or are my guesses totally off base haha..

As for o2 sensor I actually replaced it about 2 weeks ago so I'd be fairly sad if it is the main problem.
Also never heard of the whole airgap in wires thing before so that was definitely interesting."


Problem most likely is not O2-sensor. Old one was probably working perfectly fine and replacing with new brand-new working perfectly fine part doesn't change anything as you've discovered. Most likely ground-issue given the -0.1v you measured for O2-sensor output. This causes entire O2-sensor output waveform to be depressed by about -0.25v (see #3 chart, lower-left).



This artificially low output-voltage tricks the ECU into thinking you have lean mixtures and it compensates by adding extra fuel that's not needed. The result is too-rich mixture with high HC (relatively) on your two smog-test results. Although high NOx is most likely EGR-related. You'll need to do vacuum & flow testing of various components to make sure entire system is working properly.

Swapping parts only works if the part you replaced is defective. In this case, it's not. Issue is with wiring. You can find diagrams here: https://www.autozone.com/repairinfo/repairguide/repairGuideMain.jsp?pageId=0900c152801cce2c

1. inspect O2-sensor harness-side connector, verify there's no broken wires/insulation where it goes into connector. Inspect entire length of O2-sensor harness wire back to ECU and verify there's no breaks in insulation. Measure resistance between centre-conductor and outside shielding-braid. If you've done ANY repairs with soldering/crimping, you may have shorted outside shielding to centre. Should measure NO-continuity/open circuit between centre and outside shielding.

2. re-do O2-sensor wiring. Remove all soldered sections and replace with crimp-only. If wiring on O2-sensor side has braided shielding, make sure none of the shielding shorts to centre conductor. Re-read this post and note "too rich" comment.

3. measure ECU connector ground-pins resistance to chassis-ground (bolt, bare-metal nearby). ECU has these pins as sensor signal-grounds (mostly brown and white/brown): A12, B14, C5, C7, C10

4. rent, borrow, steal oscilloscope so you can plot actual O2-sensor waveforms. Need to verify that peaks are between 0.10 and 0.85 with miniumum 8-swings in 10-seconds.
 

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Measure resistance between centre-conductor and outside shielding-braid. If you've done ANY repairs with soldering/crimping, you may have shorted outside shielding to centre. Should measure NO-continuity/open circuit between centre and outside shielding.
This is what I needed to know on the Celica 4afe I had, someone used wire nuts from a universal o2 to the stock harness. 2 wires, one with sheild, one w/o. No connectors or solder. Constantly was getting 25 and 26 together. I planned soldering in a connector on the harness side but didn't know where everything went.

So, could the OP post a photo of the wiring on the o2? See where it's crimped/soldered.

And the whole air gap wouldn't apply ALL the time. The Celica is a great example, it was cut on the harness side and I bought a oem o2 so it had the correct plug already on it.

So the air gap really only applies when soldering on the o2 side
 

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Discussion Starter #52 (Edited)
The first pic is an old photo and I have since fixed that really awful bend/ space issue (angled the flange more) with the motor mount (which broke the old wire and is why I replaced o2 sensor). But the wire now has the connection shown soldered and the connection for the other O2 sensor crimped about half an inch down from the one shown in the picture.

Anyways, the crimp didn't look bad but I could always be wrong. I'm probably going to eventually get a direct fit O2 sensor to know for sure it's not a wire problem (which I should've done in the first place..), also I plan to make a swappable downpipe for the header and stock manifold for smog because that would save much headache..

The second picture is the wire I still don't know the function of. The connector looked like it melted when I last looked so that could be a problem? Though it doesn't look like it does much...


As for testing grounds, hopefully I get around to it soon...
Not sure if this is a dumb question but should I test with car off, in aux or on?
 

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3s-gte in a Camry?!?
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The second picture is the wire I still don't know the function of. The connector looked like it melted when I last looked so that could be a problem? Though it doesn't look like it does much...
That's the secondary ground for the engine. If that is burned, it means you have a problem with your main ground! Check the ground connection that goes from the battery to the top of the trans and to the side of the engine bay. Also, the auto's should have a third ground connection from the front of the transmission (radiator side) to the frame rail under the battery.

-Charlie
 

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Discussion Starter #54
The second picture is the wire I still don't know the function of. The connector looked like it melted when I last looked so that could be a problem? Though it doesn't look like it does much...
That's the secondary ground for the engine. If that is burned, it means you have a problem with your main ground! Check the ground connection that goes from the battery to the top of the trans and to the side of the engine bay. Also, the auto's should have a third ground connection from the front of the transmission (radiator side) to the frame rail under the battery.

-Charlie
Oh shoot, thanks a ton! I'll have to thoroughly check that out first then before anything else. If I have to replace it, would any wire do? Or is there a p/n for it.
Not sure if I'd have to replace it but I remember the connector's plastic housing melted.
 

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Wait, what?
I put a universal O2 replacement on a 95 V6 about ten years ago, soldered it the wires and it's still working fine. The air which is sampled does not come from the wires, just look at a cross section of a wideband O2 sensor. That line sounds like a parts droid excuse to sell the more expensive one. The one I used came with crimps, the rear bank plug was hard to get to so I crimped and soldered it and then sealed it with heat shrink.
 

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If I have to replace it, would any wire do?
I'm sure there's a PN for it... but it is probably long out of production. Any section of wire that is the same size or larger will be fine in place of the factory piece. My Alltrac has a short section of 4-gauge wire there, which is probably overkill - but it was leftover from some other project.

-Charlie
 

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Discussion Starter #57
I'm assuming these are the ground locations. I traced the wires and they all seem to be both snug and break free but I'm also not sure what I should be checking.

Pardon my ugly thumb btw lol.
 

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I'm assuming these are the ground locations. I traced the wires and they all seem to be both snug and break free but I'm also not sure what I should be checking.

Pardon my ugly thumb btw lol.
Don't need to trace, just measure resistance end-to-end.

You need to measure resistance between both ends of each ground wire with all others. So if you have two wires, you'll have four ends and four measurements to make. They should all read zero ohms or full continuity. Also measure resistance to chassis ground from all the terminals on ECU harness connector that is a ground. If all different ground points don't have full-continuity 0-ohms, you'll have ground-loops that'll cause inaccurate sensor readings.
 

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Discussion Starter #59
Ah okay thanks. I'll have to check soon, unfortunately father's day is coming up so lots of stuff happening haha.

Also I went driving and my cel turned off on its own so that's a step in the right direction.
 

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Here's picture of various ground points.




You'll want to measure resistance between each point and it should be 0-ohms:

EA -- ED
EA -- EC
EA -- EB
ED -- EC
ED -- EB
EC -- EB

Also even more important, resistance of each ECU connector terminal listed above to chassis ground. All should be 0-ohms as well. Measuring impedance is really only way to determine a wire's ability to conduct electricity. You can look at wire and it may look perfectly fine, but is completely corroded and useless underneath. If you really want to just do visual inspection, you must peel off all insulation for a good lock, then put it back on.





Some basic background into on ground loops: https://en.wikipedia.org/wiki/Ground_loop_(electricity)
 
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