BinaryJay

I thought it was the drivers side, Lexus told me it's the passenger side. Anybody know for sure what side cylinder #1 is supposed to be on?

I'm still having rear O2 sensor issues on Bank 1, getting all sorts of probably wrong advice about it and I think I need to get in and look at everything myself. Last I was told it was exhaust leak causing it, but the muffler shop said they couldn't find any evidence of that.

So now I'm back on thinking it is a water issue causing a short in the wiring as it seems that this code is always coinciding with water somehow (heavy rain, car washes). Right now, I'm thinking that since the outside parts of the wiring look fine to me that there is water getting somehow on the inside where the interior harness is.

So, if I'm going to go pulling up carpets I want to nail down what side first -- if it is the passenger side does anybody know where the harness is? Is it near the center console up front on the passenger side under the carpet? If so, what on earth could cause water to get up in that location? The actual rubber boot where the sensor wiring passes through the floor seems snug and secure.

Now I found this:
http://www.cadillacfaq.com/faq/tsb/d...-06-04-062.pdf

Apparently it seems other vehicles have problems with the ENGINE side harness, which I take to mean that there is a connector from the interior harness that the O2 sensor connects to and to the ECU itself... I don't suppose anybody has any tips on how I can find and check such a thing?

This is the best I could come up with so far in google, on a different car entirely, on what it might look like:

chuckGS350

If your engine is 2GR-FSE / 3GR-FSE (06GS300), the engine bank #1 is on the passenger side.

B1 B2

C5 C6
C3 C4
C1 C2

Front of the car.

BinaryJay

Yup 3GR-FSE, I read a bum post elsewhere on CL regarding 3GS that said it was on the drivers side I guess... I replaced that sensor already, and it wasn't cheap from the dealer... oh well, I really don't think it's the sensor anyway.

chuckGS350

Possible cause for P0138.

ibidu1

iTrader: (1)

Honestly your best bet, take the car to a good mechanic. Do not take it to the dealer! You will end up paying a butt load trying to track the problem. It would be best to find an independent shop, have him do real diagnostic work. A good mechanic will test the parts before replacing, a parts slapper is a mechanic that doesnt take his time and gambles with the parts and your wallet.

All your doing now is guessing! A good mechanic can find the problem, and it maybe even something very stupid cheap. But ask around!

BinaryJay

Only reason I took it to the dealer was to rule out the possibility that a cat or ecu was going bad that side, I was hoping that's what they would tell me since it's still covered on emissions warranty until september.

But yeah, I'm going to pay more attention to the conditions when this happens (after rain, after car wash) particularly to really nail down whether it is water related or not. If it is, then at least I know that there is a problem with water getting into a harness or a piece of wiring that is bare somewhere and it'll be easier to figure out.

All I know is that water definitely seems to be a common denominator here... and I'm leaning towards the car wash with the underbody spray causing it to pop up for a while afterwards and then it drains/dries out and is okay again. It's just the problem of figuring out where the water is causing the problem... I was feeling relieved when the dealer told me exhaust leak, then not so relieved when they told me that they can't really tell me or show me where because they can't actually see or hear it (wth?), then the muffler shop telling me they can't see or hear anything wrong but would want me to leave it overnight to check it all cold (major pain for me). First time the code came on was flash flood storm, drove through some major puddles... latest time was the day after a car wash... in between times, I have no idea wasn't paying a lot of attention to the surrounding circumstances. All I know is I should be able to bring it to Lexus and have them figure it out and not have to think about this crap myself but I guess that is asking too much of them.

My car only has like 65,000 miles on it. With this and the whole latest carbon fix the US guys are getting (but not me, well... so far... hello, Lexus Canada are you awake?) I'm really fighting my flight away from lexus reflex lately. Of course, I also feel bad for the situation the canadian owners of the IS250 are in as well... same boat, still no paddles. And to think I went with the GS because of my up to that point unwavering trust in toyota being pretty rock solid at least until really high mileage over something that would have actually fit my needs better like a vw/audi wagon.

ibidu1

iTrader: (1)

Funny you throw in VW and AUDI, they both have the same Carbon Build up issues. Google! Plus I used to own a VW and Audi tuning shop many years ago and let me tell you reliability and german do not go to together lol.

It sounds like you may have a bad connection to the o2 sensors. What you could do is grab some electrical cleaner spray, and die-electrical grease. Jack up the car on jack stands reach into the exhaust and follow the o2 sensor to the plugs, clean and grease each plug. Very easy and doesnt take much time. Matter of fact since your car sees a lot of snow. I would do it to most wiring on the car, just to help. Mas sensor, make sure throttle body is cleaned, just go through the car.