oil wicking up my o2 sensor wire harness?

[dta1984]

Just a small update. I replaced the passenger side upstream sensor and the P2238 code went off. A hundred miles later P0136 came on, so I replaced the passenger side downstream. It's now been 1500 miles and both codes have stayed off.

Now, I am getting a P0430 intermittently. Mostly while on the highway. Seems like this may lead to driver side downstream sensor. I'll probably pull the connector and clean the fluid out of it first.

 

[BoostinZX]

Another update from me as well.

I blew out the ECU connections with electronic cleaner and compressed air... Plugged everything back up and no issues for 6k miles so far... I still have not spliced in the solid cable to the o2 sensors or air/fuel sensors, but I am planning on doing that once I can find some time and the weather warms up. I suspect the air/fuel sensors will be full of fluid again when I go to do that service in the spring, but so far so good.

I hope some of you others are having better luck as well!

Mine seems to become worse in the warmer months for some reason, or it just always seems to come back in the summer due to time?

 

[gm350reratliff]

I got the internal trans harness and the pan gasket a week or so ago, now I just need to find the time to get this done. I might be doing the same to an FJ that has the same thing going on, maybe even replacing the entire harness. I'll keep everyone updated.

 

[gm350reratliff]

For anyone that’s interested, I replaced the internal trans harness and the entire engine harness on my buddy’s FJ. The repair took a whole day to complete. In order to replace the engine harness, I had to remove the upper intake manifold, alternator, and AC compressor (just moved it out of the way, no need to discharge). For the trans harness, I used a new pan gasket and about 6 quarts of WS fluid. I pulled apart the ECM and cleaned it out with electrical contact cleaner. Here’s some pics I took along the way.

I still need to do the trans harness on my 4th gen someday.

 

[BoostinZX]

Any updates from anyone on this? After cleaning the connections on my ECU months ago, i haven't had any issues... I am still planning on putting it up on a lift soon now that the weather is getting better and putting in some solid cable inline from the transmission sensor to stop the fluid, just haven't yet.

 

[dta1984]

Any updates from anyone on this? After cleaning the connections on my ECU months ago, i haven't had any issues... I am still planning on putting it up on a lift soon now that the weather is getting better and putting in some solid cable inline from the transmission sensor to stop the fluid, just haven't yet.

Ever since I replaced both passenger side 02 sensors, the lean codes have been off (roughly 5000 miles). Only code I get is a P0430 every 500 miles or so. I clear it and it stays off for a while. Getting a consistent 16.5 MPG, about 80% city driving. That's about 2 MPG below what I got before all of the issues began (note that since that I have gotten bigger tires...so maybe I am about 1 MPG below normal).

 

[Claghorne]

O2 sensor mystery possibly solved

I have a 04 Limited Runner. V6 with 225k miles. I have been dealing with O2 sensors got bad for the past year. Yes I went through 2 MAF's, feared bad cats, numerous O2 sensors, cleaned oil out of the ECM....and still was popping codes and then I went to work on a vacuum leak. I removed the PCV valve (positive crankcase ventilation valve) and it was so bad. $4.99 on a new one and the car runs like day one. Anyone interested in chatting about this message me and I can walk you through the procedure. Also I have NO CEL and car runs great!!

 

[BoostinZX]

Thanks for the update Claghorne,
I had swapped my PCV back when i did the timing belt about 5 years ago... I went ahead and ordered one and swapped it per your recommendation, but my old one seemed to be functionally working fine. I left the new one in just to see though, maybe it was intermittently sticking or something? Can't hurt for such a cheap part

Side Note: I have been driving since the last update after blowing out all my ECU connectors and cleaning them really well, and its been running perfectly fine. My gas mileage is a little off (but i did also do a lift and tires). I will keep posting in here as I do other things to try and fix it if this didn't fix it for good... So far (knock on wood) no check engine lights or any lean/rich short or long term fuel trim conditions that are very abnormal on the Torque app.

I have a 04 Limited Runner. V6 with 225k miles. I have been dealing with O2 sensors got bad for the past year. Yes I went through 2 MAF's, feared bad cats, numerous O2 sensors, cleaned oil out of the ECM....and still was popping codes and then I went to work on a vacuum leak. I removed the PCV valve (positive crankcase ventilation valve) and it was so bad. $4.99 on a new one and the car runs like day one. Anyone interested in chatting about this message me and I can walk you through the procedure. Also I have NO CEL and car runs great!!

 

[BoostinZX]

Probably unrelated, but after swapping out the PCV valve and driving the car 200 miles, my dash lit up again... Checked codes and its P0174 again... Going to pull the connector in the ECU and clean it out again to see if that helps... UGH!!!

 

[BoostinZX]

Probably unrelated, but after swapping out the PCV valve and driving the car 200 miles, my dash lit up again... Checked codes and its P0174 again... Going to pull the connector in the ECU and clean it out again to see if that helps... UGH!!!

Another Update:

I cleaned out all the connections in the ECU again as well as the connectors on the front left and right bank Air/Fuel sensors. I also added some dielectric grease to those connectors on the Air/Fuel sensors, and the Bank 2 is still dumping fuel

It seems that my issue may be deeper? or has caused the Bank 2 sensor to fail again? It didn't seem to have much oil in the connection if any at all.

This is starting to get annoying... I really don't want to sell it, but beginning to think I would be better off...

 

[j4run]

I've been following this with interest - thanks for all the info and updates. Must be incredibly frustrating.

Interesting note about the dielectric grease. If the key problems are caused by fluid wicking through wires and connectors, couldn't you _fill_ the connectors with dielectric grease to stop the flow? I don't mean lubricate them, but literally fill them so there are no spaces for capillary movement. I'd probably fill the insides, close the connectors with grease squeezing out, then coat the outside so it was a sealed unit.

This is routine for e.g. underground sprinkler system connectors. It wouldn't address the cause, but might fix the symptoms.

 

[BoostinZX]

I've been following this with interest - thanks for all the info and updates. Must be incredibly frustrating.

Interesting note about the dielectric grease. If the key problems are caused by fluid wicking through wires and connectors, couldn't you _fill_ the connectors with dielectric grease to stop the flow? I don't mean lubricate them, but literally fill them so there are no spaces for capillary movement. I'd probably fill the insides, close the connectors with grease squeezing out, then coat the outside so it was a sealed unit.

This is routine for e.g. underground sprinkler system connectors. It wouldn't address the cause, but might fix the symptoms.

Yeah I filled them up quite a bit before I put them back together... It is a very frustrating issue that I hope I can fix soon. I have a company car which helps a lot, but would be nice to be able to enjoy my new Bilstein TRD suspension and tires on the weekends

 

[BoostinZX]

Just another update. Cleaned all connectors even on the o2 sensors and cleared codes multiple times... code finally stayed off for a bit, but watching my fuel trims i'm still dumping fuel on bank 2... Something has to be causing my o2 sensors to slowly fail... i definitely have oil in my ecu and connectors but not much at all... i'm thinking it has to be a secondary issue at this point and that there is something causing my o2 sensors to go bad overtime on that bank for whatever reason... any ideas?

 

[earthrealm]

keenly watching, have had high LTFT about 18% for some years now, car runs ok, now it has jumped to 30, and a CEL P0174.

 

[That_Titanium_4RNR]

I have a 2006 with a v8. mine started leaking trans fluid from the line at some point a few weeks ago. First noticed a light trail of smoke one night when I was walking away from the truck, but wasn't sure where it was coming from. I also had a P0606 P0156 and P0157 code show up along with the christmas tree lights. A few weeks passed (now current time) and it was at the shop for an unrelated issue. They said they noticed the lines leaking so they are going to replace them tomorrow. I got under it myself this past weekend and noticed the lines they were telling me about. Looks like the fluid managed to drip allllll over my passenger side lower o2 sensor. The wires coming out of the sensor were definitely saturated. However I didn't check the electrical plug to see if the fluid had wicked up. I will check that tonight. I am thinking this trans fluid caused my cel codes and fried my o2 sensor. I also feel like my fluid wicked up to the ecm but I have yet to check that too....where exactly is it located?

 

[BoostinZX]

Just another quick update. I don’t drive the car as much anymore but I’ve been throwing p0172 & p0175 codes left and right here lately.

Oil still showing up in ecu (never did the splicing of solid cable from the trans)

Checked again for air leaks. Only new thing that may be possibly introducing the issue is I’m getting some ticking from the exhaust manifolds. So those are probably cracked now. Not sure if that may be part of the issue or not.

Replaced MAF again just for the heck of it and no change. Went with OEM this time even though the previous replacement was Hitachi which is OEM.

Definitely something happening before the front A/F sensors to cause both banks to throw the code. But I’m sure after driving it with the codes and the fuel trims off bad that they are nice and carbon covered at this point.

Anyone else with anymore updates or long term fixes?

 

[BoostinZX]

Still dealing with the same issues. The car stays parked most of the time and I really don’t want to give up on it. But starting to lose faith. Anyone else have any luck?

 

[white_lx2]

Thank you to everyone who contributed to this thread. It was really helpful in diagnosing my intermittent lean codes on my 2008 GX470.

I had found some oil in the A/F sensor connectors, but thought is was from the Fluid Film undercoating at first. The yellowish color of the oil that I found was also sending me off in a tangent. Here is some more information Oil wicking into ECM - random A/F sensor codes P0171/P0174/P2195/P2197 | IH8MUD Forum

 

[BoostinZX]

I have about given up on mine, but looks like i need to get underneath and check that connector. Mine has gotten bad enough to even shut off randomly while driving it, normally when turning which is super fun/safe. Thanks for your post [MENTION=760255]white_lx2[/MENTION]!

Thank you to everyone who contributed to this post. It was really helpful in diagnosing my intermittent lean codes on my 2008 GX470.

I had found some oil in the A/F sensor connectors, but thought is was from the Fluid Film undercoating at first. The yellowish color of the oil that I found was also sending me off in a tangent. Here is some more information Oil wicking into ECM - random A/F sensor codes P0171/P0174/P2195/P2197 | IH8MUD Forum