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- #21
Quick update. First test drive results look promising. Here is a part of a data log of the total fuel trims (STFT+LTFT) for both banks (logging with Tactrix Openport). No longer any strange excursions from the 'normal' values.
Oil wicking into ECM - random A/F sensor codes P0171/P0174/P2195/P2197 (1 Viewer)
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- #24
I still haven't started replacing mine, but thank you for being so thorough on your posts! Any update? fuel trims still looking good? And care to share the 3d print for the A/F connectors?
Everything looking fine so far. I have not yet connected a scan tool to see if there is any fuel trim creep, but I don't smell the rich exhaust anymore. It has been running great. Probably put around 1000 miles on the vehicle since (don't drive it a lot).
Once diagnosed, it was actually a pretty easy fix. By replacing the internal transmission harness the wicking should have stopped. Without the pumping action, the ATF might just remain in between the wire strands. I did leave the A/F sensors unplugged for a few days during the repair and the connectors stayed dry after cleaning them out.
Sure I can share the 3D print. Not sure how to. Email? I'll pm you my email address.
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A big thanks to everyone here. I have had a saga of similar issues, I fired the parts cannon based on different codes and engine behavior before finding this thread. What a relief to pull the locking handle on the transmission wire harness and pull it out to see transmission fluid literally drain out of the wire harness. It was like popping a blister after a 1/2 marathon in the same sense that the healing can start. Parts arrived this week and I started working today. Got the wire in and put a new filter and gasket while I was there. 2 of 20 transmission pan bolts were broken when I bought my 2005 GX470 (215K miles, nav, air shocks deleted, fairly stock no big mods) and I managed to break a few more despite a long soak and hand removing bolts so I just ordered 20 new ones. Maybe the last guy to drop it didn't use a torque wrench or I just bad luck but the broken ones will be easy to remove.
One tip I want to share is: I stacked 3 pool socks in the nozzle of my shop vac and taped them down. I then pulled wire harnesses at the ECU and vacuumed a surprising amount of transmission fluid out, the pool socks were used to catch the fluid without restricting the air flow and they did a great job. I'm repeating this vacuuming at different sensor wire connections in the next few days in the hopes of 'drying up' the wiring enough so there are not more issues in the future.
If I have to do this job again I'm definitely removing the shaft in the way of the connector bolt, I wear a XL glove size and barely reached up in there to get the job done. I took photos of the wire routing per suggestion here and it saved me from doing it wrong, so I second that suggestion. The rest of the job went fairly easy.
I can't wait to get back behind the wheel, hopefully my bolts from Lexus Parts Now get here in a reasonable time.
One tip I want to share is: I stacked 3 pool socks in the nozzle of my shop vac and taped them down. I then pulled wire harnesses at the ECU and vacuumed a surprising amount of transmission fluid out, the pool socks were used to catch the fluid without restricting the air flow and they did a great job. I'm repeating this vacuuming at different sensor wire connections in the next few days in the hopes of 'drying up' the wiring enough so there are not more issues in the future.
If I have to do this job again I'm definitely removing the shaft in the way of the connector bolt, I wear a XL glove size and barely reached up in there to get the job done. I took photos of the wire routing per suggestion here and it saved me from doing it wrong, so I second that suggestion. The rest of the job went fairly easy.
I can't wait to get back behind the wheel, hopefully my bolts from Lexus Parts Now get here in a reasonable time.
Hoping my experience could help someone.
My 2006 LX470 had trans fluid wicking into the wiring harness. The point of entry was a white plug on the driver's side about right between the shifter and the gas pedal. This is very easy to get to/check and we blew it out and put some white/translucent electrical contact solution in until I could get the parts and work toward replacing the harness.
This was discovered one day because the truck wouldn't shift into overdrive. Luckily within a few days I had it in front of a mechanic who specializes in LC/LX who identified the issue.
I purchased the internal and external wiring harnesses for the transmission and had both replaced with OEM for fears of the wiring harness being saturated and seeping all the way into the ECU which, based on this thread, has happened. The harness comes with a new plug/portal into the transmission so any existing point of failure were eliminated.
That was ~7k miles ago and no issues since. It is noted the upper end of the trans wiring harness where it snaps into the main harness was thankfully dry so I don't believe any fluid made its way up.
I cant remember if it threw any codes or just the fact that it didn't shift into OD was my trigger but this is my experience and again, hope this helps.
My 2006 LX470 had trans fluid wicking into the wiring harness. The point of entry was a white plug on the driver's side about right between the shifter and the gas pedal. This is very easy to get to/check and we blew it out and put some white/translucent electrical contact solution in until I could get the parts and work toward replacing the harness.
This was discovered one day because the truck wouldn't shift into overdrive. Luckily within a few days I had it in front of a mechanic who specializes in LC/LX who identified the issue.
I purchased the internal and external wiring harnesses for the transmission and had both replaced with OEM for fears of the wiring harness being saturated and seeping all the way into the ECU which, based on this thread, has happened. The harness comes with a new plug/portal into the transmission so any existing point of failure were eliminated.
That was ~7k miles ago and no issues since. It is noted the upper end of the trans wiring harness where it snaps into the main harness was thankfully dry so I don't believe any fluid made its way up.
I cant remember if it threw any codes or just the fact that it didn't shift into OD was my trigger but this is my experience and again, hope this helps.
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- #27
Thank you for posting this here. The '06 LX470 has the same A750F transmission as the GX470's and I always wondered if the wicking could occur on LX's as well. Since the production numbers are so much lower than the GX, we are probably not seeing as many cases. Very smart of the mechanic to identify the problem so quickly. I'm wondering if it so common, that he knew to look for it right away.
My mechanic said he’s only seen it happen 2x, me being 3rd, and almost exclusively works on Land Cruiser platforms for the last ~20 years.
Just to also provide some context on trans harness issues, I ended up with P2759 codes in my GX earlier this year. Using a multimeter and the FSM procedure I isolated it to some harness splices I had made for my WAT lockup switch and the harness inside the trans. The harness inside the trans is actually pretty easy and cheap to replace (around $60). My overall shift performance improved quite a bit, TCC lockup is much smoother, and some "funky" things the trans would occasionally do (clunking when shifting gets under some throttle conditions - such as merging onto the interstate) also went away. I certainly didn't have the wicking problem, but had other harness-related problems.
IMO the harness in the A750F is really a wear item and I'd recommend replacing it on most of those as they get north of 150K miles, perhaps as part of a trans fluid change. I had to remove the front driveshaft to get good access at the connector for mine, which was not a huge problem. The harness part number has also been updated by Toyota and does not exactly match the old harness, which did add some confusion to my install.
IMO the harness in the A750F is really a wear item and I'd recommend replacing it on most of those as they get north of 150K miles, perhaps as part of a trans fluid change. I had to remove the front driveshaft to get good access at the connector for mine, which was not a huge problem. The harness part number has also been updated by Toyota and does not exactly match the old harness, which did add some confusion to my install.
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- #30
Update: plugged in a scan tool today and performed the A/F sensor active test. Both A/F sensors still responding normally. About 3000 miles since the repair and 255 full warm-up cycles. (Diagnostic report from Topdon Topscan. Highly recommended low cost bi-directional VCI communicating with your phone. I just find it so much easier to do a quick test compared to using Techstream.)
