Dash Lights and Code P0136, Need Advice (1 Viewer)

[Hodence]

Hi all! My 2004 UZJ100 LC has had some dash lights on for a bit, I finally got my a** in gear and scanned the OBD2 port, and got code P0136. To be more specific, the CEL was on along with "RSCA OFF" and "VSC TRAC". First off, I'm assuming the two latter lights aren't connected to the code since P0136 is an emissions-related code but correct me if I'm wrong there.

My current running theory is related to an incident that happened roughly two years ago when on a road trip, the O2 sensor on the driver side by the transfer case came out of its bung and hung in the fresh air. The problem was quickly noticed when the car felt down on power and fortunately, some friendly diesel mechanics offered to take a look (despite it being a gas car) and found the hanging O2 sensor and put it back in. It immediately solved the problem, but the car ran quite rich for maybe 5-10 miles. That might have ruined my catalytic converter. As well, the vehicle has had an exhaust manifold leak in the past although I can't hear any noise currently. I'm thinking these may be the reason for the code, but open to suggestions.

Are there some common causes for the P0136 code or anything I could check? Hoping to solve it this weekend, but aren't we all?

Any advice on the lights or codes is very welcome.

 

[Hodence]

I was mistaken on the lights. It’s actually “VSC TRAC” and “VSC OFF”.

 

[RND1]

That code is for an O2 sensor. Crawl under it and look at driver and passenger sides. It will be obvious. Likely the same driver side O2 sensor. Common for these to rust out. $50 and 10 min and you're back in biz.

Amazon product ASIN B000C5SG8G

 

[Hodence]

O2 sensor ordered! I also read that the issue with the sensor can cause the VSC TRAC and VSC lights to come on. I'll report back after I install the sensor and clear the code.

Also, side note, I found in my service history that the catalytic converter that would've been damaged by the O2 sensor falling out was actually replaced, so I'm all good there

 

[RND1]

O2 sensor ordered! I also read that the issue with the sensor can cause the VSC TRAC and VSC lights to come on. I'll report back after I install the sensor and clear the code.

Also, side note, I found in my service history that the catalytic converter that would've been damaged by the O2 sensor falling out was actually replaced, so I'm all good there

Any time you have a CEL, the VSC TRAC, VSC OFF, and BRAKE lights automatically turn on.

Good news on the the cat replacement, those aren't cheap! As I said in your other post, it looks like you got a well maintained rig.

Heater tee's are the most important maintenance item for you right now. If they let go while you are out driving, bye bye engine.

 

[Hodence]

I ordered the heater t's along with the o2 sensor, so they'll both arrive tomorrow. There's still a chance I can get the problem solved by the end of the weekend!

If a heater T goes while I'm driving, will it dump coolant? Because now that you've said that, I want to know what to look out for. I'm assuming I'd see a rapid increase in engine temp and maybe be able to catch it, or is it like instant engine destruction?

 

[jOnathN]

If the exhaust manifold is leaking significantly it can throw off the O2 sensor also. Think it has to be a sizable leak though.

 

[RND1]

If a heater T goes while I'm driving, will it dump coolant? Because now that you've said that, I want to know what to look out for. I'm assuming I'd see a rapid increase in engine temp and maybe be able to catch it, or is it like instant engine destruction?

Depends on how bad the T breaks. If you don't catch the increase in temp and keep driving (which is easy to do), head gasket will blow or worse.

Usually they crumble apart upon replacement.

 

[Hodence]

I have an update on the O2 sensor issue! And I don't know if it's good or bad. My OBD2 reader is a Fixd, and when it scanned and gave me the code P0136, that's already been covered in this thread. When Fixd scans your car, it'll give some info about the code, it described it as a downstream sensor malfunction in both bank 1 and bank 2 at separate points in the article. I did some research and it seems like everyone says bank 1 (driver's side), so I replaced that O2 sensor with a brand-new Denso and cleared the code. I've only idled it for maybe 10 minutes, but enough to look at some live diagnostics from the Fixd. You can see the O2 sensor voltage results below.

As you can see "one of these things is not like the other". O2 sensor 2 "warmed up" (first pic) and then stayed incredibly steady at about 0.6V (second pic). So I don't think this fixed the problem although I forgot to look at the data before I swapped them, so it may be different. I haven't had the CEL come on yet, but I expect it to. Certain websites say that the downstream O2 sensors should flatten out, but I think that's after the cat warms up.

If anyone has any advice, please let me know. The electronics of this car scare the sh*t out of me, but I ought to learn at some point.

 

[Hodence]

A little update; I ran the live data tool and drove the car around my block a couple of times. The Sensor 2 values did change and did so accordingly (voltage increased when I stepped on the throttle and decreased when I lifted). It's just weirdly smooth compared to the other sensors. Now I'm wondering if there's another sensor that's supposed to be reading smoothly and isn't. As usual, any input is greatly appreciated!

 

[Hodence]

Alright, this is hopefully the last update on this thread for a while. I took the vehicle with the new o2 sensor on a ~300-mile shakedown run. The CEL hasn't come back on and my fuel mileage went from about 14.5mpg highway to 17.6mpg. The engine sounds and revs a little smoother, so things seem to be looking up. I just wanted to add this last update for anyone on the thread with this same problem. I'll update this thread if the CEL comes back on or if there are any other significant changes in the situation. Thank you, everyone, for the advice, and thank you RND1 for the link to the sensor, that was the one I used and it fit great.