P0136 - Oxygen Sensor Bank 1 sensor 2 malfunction

CEL came on over the weekend returning code P0136. Trying to read through all the posts regarding it, I think I'm gonna go ahead and change out the sensor since it has 214k miles of use. Just hoping someone can confirm I will be ordering the correct part before dropping the money. Also, so I can work on it this weekend, I would prefer to either get one locally or order through amazon. Or should I just try and find the time to install next week and wait for the "dealer" part. Prices all seem the same, just shipping times.

Thanks.

Dealer O2 Sensor 89465-47080

Amazon Denso O2 Sensor 234-4400

Here is the live data of my commute home reading just that sensor:

 

Thanks! I didn’t realize it could be cleaned. Unfortunately I already ordered the amazon one and will be here tomorrow. Of course on my way home last night, the CEL turned off. Did another scan and that code is pending again.


-Spiral

 

I wasn’t completely sure if that was because it was purely inverter engine at that point. That’s where I was transitioning from one highway to another

But either way, I’ll install the new one since I got it and it’s a pain to do just for a cleaning


-Spiral

 

Both things good to know. I had read about changing the front sensor from some other threads, so that is on the radar, but didn’t really wanna drop $260 for two sensors at once if just the rear was bad.

I just went out and checked the exhaust manifold from the old engine and they did reuse both sensors. Hopefully they verified the front sensor was not covered in junk when they reinstalled it. When they installed the engine I asked them to verify the cat was in good shape and if they said it was and it fails in the “warranty” it would need to be on their dime. They agreed so I am assuming the cat is not our problem and just sensor issues.

It didn’t arrive Friday like they said, so I wasn’t able to change it over the weekend, so I’ll just have to find time this week after work.


-Spiral

 

I thought I'd update this thread, unfortunately not for the better. Since June when I first posted, the CEL actually had turned off on it's own for about 3 weeks. When it turned back on, I replaced the downstream O2 sensor during my regular oil change since the car was already on the lift. The car seemed to actually drive a lot smoother for 1 day. Day 2, CEL came back on with P0136. Here is the slight interesting thing, my fuel economy, which usually averages 36 mpg, was improving. I started seeing 38, 39 and even 40 mpg average during my commute (all highway mind you). The CEL started to grate on me a bit, so I broke down and purchased the Air Fuel Sensor (upstream o2). Got it installed yesterday, which in itself was a PITA. Either my ratchets were too short making it difficult to get leverage, or my breaker bars were too long and couldn't get any movement. Eventually i figured out an angle and hand placement to knock it loose. With the old one out, I tested the leads according to page 1992 of the manual and got 2.4 Ω for HT/B, and got OL (greater than 10 kΩ) for HT/AF-, so does that mean the old one isn't bad?? Got the new one installed anyway, cleared the code, drove to the auto store to return the o2 sockets, Mother &$#*er the CEL came back on with a P0136 code. Just ran out and looked at the voltages again and the A/F was at 3.3v with some fluctuations, Fuel Trim was between 0 and -2%, but the downstream O2 is showing (zero) Volts (which after reading may be due to the CEL being on). Could I have destroyed the downstream sensor over the last couple months? I didn't think to test the sensor resistances until this morning.

So my plan is to:
Test Resistance of Heated Oxygen sensor (ht1b/b 11-16Ω, ht1b/e2 >10kΩ)
Test Voltage of the Heated Oxygen sensor Harness (11-14v)
Test Resistance of Air Fuel sensor again (ht/b 1.8-3.4Ω, ht/af >10kΩ)

If those test accordingly, according to p2301, the only other things left would be exhaust leaks or EGR valve? Gawd I hope that's not the case. It's only been 24k on this "new" engine with supposedly cleaned EGR system (not sure I believe that Lexus actually did this). Thankfully, my old system has been cleaned and I can swap it in if i have to. Open to any other suggestions.

 

the video above that The Critic posted did a good job explaining why the A/F sensor would lead to a downstream sensor thrown code. I don't know why i didn't take the time to actually test either of the new sensors, guess I was just being lazy or too much blind faith. Both the sensors are not labeled "toyota", but are Denso and were priced the same. So it just came down to easy shipping from Amazon vs waiting on a dealer. I'm not really looking forward to removing the underbody paneling again to get at the AF sensor just to test it.

I think I'll try clearing the code and recording the live data on my drive home to see if/when it fails.

 

well crap:

The Heated O2 sensor for downstream was the one I posted above. 243-4400
The air fuel sensor was 234-9090.

double crap. Looks like I got the correct one for the downstream, but the air fuel should have been 234-9112. Guess that's what I get for trusting Amazon to tell me "this part fits your vehicle". Strangely enough, the 9090 was visually the same size and harness fit perfectly.

I guess I'll try and order the 9112 instead. Thanks Critic!

update: I guess the 9090 fits the 2015-2016 model years.

 

2012. The toyota number on the part itself is 89467-62060. all the sites to plug in vin numbers are acting funky for me right now. I'll have to come back and check later.

 

could that contribute to the code coming back right away even if the sensors are working properly?