oil wicking up my o2 sensor wire harness?
- Thread starter turbo sol
- Start date
Alright, so I have been chasing down 02 codes and lean codes (p0174, p0171, p0136) for over a year. Replaced both downstream 02 sensors, a/f relay, and all general tune up stuff (plugs, cleaned maf, pcv, tb clean). The codes would always come back....sometimes not all 3 at once.
A deep Google search last night and I came across this oil in wire harness phenomenon. A light bulb clicked and I remembered last year while replacing one of the 02 sensors, there was moisture in the plug. So sure enough today, I pulled the top 3 plugs from the ecm and there was red-brown oil on the second and third plug.
[MENTION=66389]BlackWorksInc[/MENTION], any idea which sensor may be wicking moisture?
Can someone give me a diagram of this harness?
@OP if you're still around, what was your solution?
Here is my original thread; http://www.toyota-4runner.org/4th-gen-t4rs/222402-02-sensor-check-engine-lights.html
A deep Google search last night and I came across this oil in wire harness phenomenon. A light bulb clicked and I remembered last year while replacing one of the 02 sensors, there was moisture in the plug. So sure enough today, I pulled the top 3 plugs from the ecm and there was red-brown oil on the second and third plug.
[MENTION=66389]BlackWorksInc[/MENTION], any idea which sensor may be wicking moisture?
Can someone give me a diagram of this harness?
@OP if you're still around, what was your solution?
Here is my original thread; http://www.toyota-4runner.org/4th-gen-t4rs/222402-02-sensor-check-engine-lights.html
Attachments
BlackWorksInc
New member
Looks like it could be transmission fluid? I am not sure... haven't seen this on a 4Runner before.
Ya, that is what I was thinking.
This link shows the sensor in the transmisison pan may be the culprit https://www.justanswer.com/toyota/6xjis-toyota-4runner-sr5-2003-4runner-chronic.html
I think I am just going to dry everything out with compressed air and see how long it takes to re-saturate, and the check engine light to come back on.
Just thinking out loud here, but what if I cut the connection from the transmission sensor as the OP was going to do. Is there a type of connection to re-join the wires that would be less susceptible to capillary action (spade, butt, solder etc.)? What about splicing in solid core wire? I know solid core wire and vehicle vibrations don't mix too well though....
Supersonic
New member
Going to add the end of the link so everyone knows what's going on. Thanks for posting all this it's very mysterious and I wish you the best getting through it so you can drive your 4Runner again with confidence.
BoostinZX
New member
I am very interested in how this turns out. I have had similar intermittent issues driving me crazy. I have replaced the A/F sensors and O2 sensors, just to have them go bad in a few months. The car intermittently will run like crap, and then will run fine for a few days/weeks/months, etc... and then run bad again... I'm thinking this may be a very possible culprit to the root of all my problems... Thanks for bringing it to my attention dta1984! Please keep us posted on the progress and ideas!
Thanks for posting that! It does clear up what I was referring to.
Hey no problem! Glad to see it may be the root of your issues as well. Our symptoms are very similar.
Most likely it will be this coming weekend i'll get back around to working on it. My intention is to first blow out all of the connectors and ECM, and see how long that lasts me. Next step will probably be to splice the wire somewhere to see if I can stop the capillary action.
gm350reratliff
New member
I'm still find it hard to believe that the transmission fluid is getting pushed through the wiring harness, especially the O2 harness, and into the ECM. I don't recall ever seeing that on any of the vehicles I've worked on. I would think you would see one of the connectors between the transmission and ECM start to leak first. Plus, if the connectors are dry inside, there's no way that's the issue.
It's funny that this thread popped up because a friend of mine was dealing with some lean codes on his super clean, pampered FJ after the dealer forgot to put the air filter housing together. He put the air filter housing back together himself but ended up taking the FJ back after the codes re-appeared. The dealer's findings were that the transmission over-pressured due to a plugged transmission vent and pumped ATF through the harness to the ECM. They recommended replacing the ECM, entire engine/trans harness to the staggering cost of $5k, and that was just to start. It didn't sound right to my buddy because they never mentioned anything about clearing or replacing the trans vent or to find out why the transmission was over-pressurizing so he had them put it back together and he drove it home. Not to mention that the FJ is driving and running perfectly fine other than the CEL was on. The dealer supposedly showed him oil on the ECM connectors but the oil, or whatever it was, had no color, it was clear. When my buddy inquired about that the dealer stated that the ATF in the FJ was clear, not red (more red flags).
I went and checked the FJ out and pulled apart several connectors (O2 and some others) and found them to be dry. I next went the MAF, since the whole problem started with the dealer leaving the air filter lid off. I cleaned the MAF and so far the CEL is off and the FJ is running great. I feel that the dealer was completely trying to take advantage of my buddy. I never dug into the ECM to see if oil was on those connectors but I really doubt oil is getting to them anyway. Like I said, it just seems highly unlikely that such a thing could even happen, much less to a low mile, very pampered FJ.
It's funny that this thread popped up because a friend of mine was dealing with some lean codes on his super clean, pampered FJ after the dealer forgot to put the air filter housing together. He put the air filter housing back together himself but ended up taking the FJ back after the codes re-appeared. The dealer's findings were that the transmission over-pressured due to a plugged transmission vent and pumped ATF through the harness to the ECM. They recommended replacing the ECM, entire engine/trans harness to the staggering cost of $5k, and that was just to start. It didn't sound right to my buddy because they never mentioned anything about clearing or replacing the trans vent or to find out why the transmission was over-pressurizing so he had them put it back together and he drove it home. Not to mention that the FJ is driving and running perfectly fine other than the CEL was on. The dealer supposedly showed him oil on the ECM connectors but the oil, or whatever it was, had no color, it was clear. When my buddy inquired about that the dealer stated that the ATF in the FJ was clear, not red (more red flags).
I went and checked the FJ out and pulled apart several connectors (O2 and some others) and found them to be dry. I next went the MAF, since the whole problem started with the dealer leaving the air filter lid off. I cleaned the MAF and so far the CEL is off and the FJ is running great. I feel that the dealer was completely trying to take advantage of my buddy. I never dug into the ECM to see if oil was on those connectors but I really doubt oil is getting to them anyway. Like I said, it just seems highly unlikely that such a thing could even happen, much less to a low mile, very pampered FJ.
BoostinZX
New member
I'm thinking it could be. I am definitely going to try cleaning out the connectors on both sides with Electronic Cleaner spray and letting it dry... see how long that keeps issues at bay. Thanks again and keep me posted! I will do the same as well if I make any additional discoveries!
I agree it's definitely odd, but it does happen. Ever since I found this thread I've been reading up more on it.
Thanks for mentioning the transmission vent, that was mentioned in the other thread. I should probably check that first.
Supersonic
New member
Where is the transmission vent located? Might just be a lazy question, but before crawling under it I want to know what to look for.
I haven't looked for it yet, but according to this link it's on top of the bell housing (at least on the v8). http://www.toyota-4runner.org/4th-gen-t4rs/127183-breather-locations.html
BlackWorksInc
New member
[MENTION=32290]gm350reratliff[/MENTION]
Like I said on a Toyota it's very odd. I think I've only seen this once before on a Camry? I could be wrong on that it's been years. But I have seen sensors fail and fill up an ECM, it was fairly common with BMWs I recall from when I did used cars and my dealer tech friend was telling me.
Like I said on a Toyota it's very odd. I think I've only seen this once before on a Camry? I could be wrong on that it's been years. But I have seen sensors fail and fill up an ECM, it was fairly common with BMWs I recall from when I did used cars and my dealer tech friend was telling me.
Is the transmission vent on top of the bell housing? I couldn't find a definitive location for it.
Thinking back, my trans pan gasket had been leaking. I did replace it, but wonder if it's linked to a plugged vent and over pressurizing.
Supersonic
New member
I found a part number (35104b) and diagram here;
https://parts.lakelandtoyota.com/sh...ake=1060&ukey_model=15455&ukey_category=21653
and Rock Auto has a DORMAN 924284 Auto Trans Case Vent Alternate/OEM Part Number(s): 9093003136
http://www.rockauto.com/en/catalog/...431016,transmission-automatic,case+vent,14361
I am going to the dealership later so in the meantime I may crawl under and look for the it.
https://parts.lakelandtoyota.com/sh...ake=1060&ukey_model=15455&ukey_category=21653
and Rock Auto has a DORMAN 924284 Auto Trans Case Vent Alternate/OEM Part Number(s): 9093003136
http://www.rockauto.com/en/catalog/...431016,transmission-automatic,case+vent,14361
I am going to the dealership later so in the meantime I may crawl under and look for the it.
Thanks, that's it! That link brought up a Tundra, but I was able to find the diagram. Looks like it is on top, and probably visible from the back of the engine bay.
https://parts.lakelandtoyota.com/sh...1653&ukey_driveLine=6776&ukey_trimLevel=18357
https://parts.lakelandtoyota.com/sh...1653&ukey_driveLine=6776&ukey_trimLevel=18357
Attachments
gm350reratliff
New member
The vent is on top of the bell housing and comes up and is attached to the rear of the driver side head. At least on my 2008 it is.
So yesterday I pulled all the ECM plugs, and both downstream 02 sensor plugs. Both downstream sensor plugs had ATF in them, in particular the passenger side was the worst. I wiped them out, used compressed air and electrical cleaner. Unfortunately within 10 miles the code came back on (P0171, P0174, P0136).
After the drive I pulled the ECM plugs and didn't notice fluid on them, maybe a little, but could have been residual.
I suppose next steps will be to first check the 02 plugs again to see if fluid already filled back up. Along with that I'll pull the ecm out completely to make sure no oil is inside of it. I also need to locate and check the transmission breather.
After the drive I pulled the ECM plugs and didn't notice fluid on them, maybe a little, but could have been residual.
I suppose next steps will be to first check the 02 plugs again to see if fluid already filled back up. Along with that I'll pull the ecm out completely to make sure no oil is inside of it. I also need to locate and check the transmission breather.
Similar threads
