P0136

Like many others I have the dreaded p0136 code. I replaced B1S2 sensor but the code continues. My code reader shows very low voltage on B1S2 .003 volts. Not much change I I increase RPMs. My spark plugs are pretty old 120000 miles maybe on them. Also showing low voltage on B1S1 but not throwing a code. Could old spark plugs cause these problems? I getting close the inspection so I either have to figure this out or take to a garage. I'm thinking a Toyota dealer will be my best bet but really hope to get this straightened out. Any thoughts would be appreciated

 

Where'd you by your part, and what brand/part# was it?

Did you pull the negative battery cable for at least 10 minutes to force a re-learn cycle after replacing?

I see the p# breakout for Denso is as follows, you're one of the years with different downstream part numbers per side:

B1S2:

$64 234-4161 Oxygen Sensor with 15.35” 4-Wire Harness

234-4161 (EDIT: Don't order any of these parts from scAmazon, forum may auto-link to them, that's the forum doing it, not me!)
B2S2: 234-4162
B*S1: 234-4169​

I normally recommend to replace in pairs (1 fails on a bank, replace both for that bank) based on other cases we've seen. But if you can't or don't want to, since the upstream are the same p/n, I'd recommend one basic test: Swap the upstream sensors B1 <--> B2. Just to verify if the code doesn't suddenly flip to P0156.

The FSM throws out the following as potential cause list, but honestly ... it's hit or miss. And we've seen cases where changing the other sensor on the failing bank resolved the issue. We've also seen cases where it wasn't the O2 sensors at all...

​

 

Thanks the reply. I replaced with denso brand. Planning on trying get B1S1 out tonight after I change spark plugs. Been soak B1S1 with penetrating oil the past few nights. Hopefully that'll make it easier to remove

 

As long a you didn't buy it on scAmazon or fleaBay, the internet's classic counterfeit parts cesspool, I'd sleep easy that it's not a faulty/knockoff part.

Sorry to advise you on doing something that'll probably bust some knuckles. I think I speak for everyone when I say, it really sucks dealing with anything ferric on exhaust within 24-36" of the block. The closer to the block you get, the worse it inevitably is.

Curious to hear the results. Don't forget to pull that neg batt cable while you're wrenching

 

Thank for the reply. I used Denso for the B1S2 sensor. I didn't replace B1S1, yet. Replaced spark plugs on Bank 1 also. They were pretty bad. I've been soaking B1S1 with Kroil for a couple of day hoping to make removal easier. Going to do try removal tonight. Also disconnected the battery. As of last night after 4 spark plug change (only did bank 1 ), I cleared codes but still had a pending p0136 code after a 25 mile drive. Disconnected the battery after that drive.

 

Sorry for the somewhat duplicate post. It didn't show up on my phone now it's there. O2 came from Napa. I pretty buy my repair parts from them exclusively. I figure it's probably the best place to get quality parts fast. I like a local guy I can go to. He might have advice I can't get from Amazon

 

I’m not insinuating Napa is the problem but when I dealt with a P0420(cat efficiency), I chose to use my local Napa dealer also. Unfortunately it would come back periodically and the voltage on a graph was similar to your low reading. Searching the part number that was on the Napa sensor, led me no where that confirmed it was a Tundra replacement. I then chose to order OEM from McGeorge, readings became more accurate and have not had an O2 problem since….YMMV

 

It's less a matter of quality of parts and more a matter of what others have found least-problematic with these trucks.

There are a few electronic parts you really want to get in the habit of only buying OEM (i.e. Toyota/Denso/Aisin).

• Fuel pump
• Coil packs
• Starter
• O2 sensors
• Cam/crank position sensors
• Relays

Two reasons being: One, in case of fuel pump and starter, you're going to get another 15-20 years out of that part buying OEM from a legitimate source, they're such a PITA to install, plus 3rd party parts aren't built to the same QC/QA level which is why you're paying less $$ but inevitably going to get stuck doing the job more often. Other being, folks have found (especially with coil packs, O2) aftermarket brands sometimes don't play nicely or end up throwing codes anyway. And with relays, a couple of visitors here found store-bought relays didn't function as intended or advertised.

There are non-electronic cases also, huge one being lower balljoints, always go OEM to avoid failure (even NAPA got hit with the massive recall for '03-'04 LBJs sold from 2020-2021), and air/oil filters are another, the OEM has been tested and proven to work better than aftermarket.

In some cases, like the MAF, Hitachi made it for Toyota, so OEM doesn't make sense, just buy the Hitachi part and move along. There's a few other "OK to go non-OEM", directly from member experience, over here.

 

So, Denson brand O2 sensors should be good to go.

 

Denso is the OEM equipment.

Denso, Aisin, Fujitsu, are three of the companies that manufacture the OEM parts in general. Aisin more of the mechanical stuff (Calipers, water pump, timing belt for example), and Denso much of the electronic/electro-mechanical (coil packs, starter, spark plugs, fuel pump, etc.) and a few other bits (radiator is an example).

To ensure you're not dealing with well-made knockoffs from unregulated/unaccountable store fronts like fleaBay and scAmazon, which are genuinely problematic counterfeiting havens, there are a few non-OEM stores online to order from, RockAuto and SummitRacing usually meet or beat the unregulated store fronts anyway in pricing, or within a couple percent. This thread also shows you how to order parts Toyota direct without paying the full, sometimes outrageous MSRP they charge you at dealership parts counters. If all else fails, order online from McGeorge Toyota's OEM dealership parts storefront, almost universally members have a great experience and get great pricing - the thread I linked also shows you how to look up your p/n, although Toyota changed the system so some content is a bit dated.

I would still hold off on ordering Denso to replace the NAPA part, just because I'm saying it, or Bubba also had issues, as have others with non-Denso for that specific part, but ... it's something to keep in the back of your mind.

 

Thanks. Anyone ever use an impact wrench on B1S1? Seems risky but I'm not sure putting wrench on there with a 10" isn't just as risky on an old exhaust system

 

@TimH
Mind showing a pic of what condition that particular sensor looks like.
We've had all kind come thru here and others can share their experience according to what yours looks like.

 

Sure which sensor, or both B1S1 and B1S2?

 

My bad, I mis-read and thought you were asking about downstream, B1S2.
Ole eyes ain’t what they use to be.

 

B1S2

 

Typical spark.plug on B1. Pretty worn maybe the cause of failure?

 

Can't really see the tip, but does look pretty tired overall. Any idea last time they were replaced?

This is one of those places where I'm still an NGK fan, over Denso. I'd probably opt for Iridium plugs (regardless of brand) just so you're not changing them for at least another another 60k-80k and they should be pre-gapped properly. Here are the OEM part numbers for your truck for Denso in standard, platinum, Iridium, and also the NGK part #s in Iridium and Platinum. Can't recommend buying online. But if you have an Advance Auto Parts near you, you can order at their site for in-store pickup, here's 15% off coupon code: RMN15

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I have no idea how many miles them. I was pretty lax in changing them. Gotta be 150000 moles if i was guessing. I did put in iridium plugs. ~$12/plug

ETA: there is no tip left. It's pretty much flush with ceramic insulator. I would say the gap has to be close 1/8"

 

Either way, I'm not convinced it would've been the current cause of that O2 circuit code though. I'd expect a misfire code before anything else.

 

That's what I thought, misfire would throw a code.


Doing B2 plugs tonight or tomorrow morning.
Considering the length of time they were in there they came out pretty easy. I was worried about galling and wrecking the threads

 

I haven't seen anyone here do that yet. One saw a plug snapped off. As long as you don't make the mistake of using anti-seize on them, you're golden.

 

I didn't use antisieze but kind of thought it might something people would do.

What are your thoughts on using an impact wrench on B1S1. Im not sure i can even get to it with an impact. 'd hate to ruin the cat though by not realizing I'm stripping the thread because I used an impact.

 

I'd bang my knuckles using a O2 wrench adapter on the end of a ratchet, with a piece of copper pipe as a breaker bar if I needed it.

 

Other than 12v for the heater is there voltage supplied to the sensor or does the sensor just produce a voltage signal sent back to the computer. It's my understanding that's how the system works, am I wrong?

 

Using the torque pro app with a graphing I can see voltage fluctuate quite a bit on B1S2 , B2 S2 (.2 volts) remains fairly steady when reving engine. White is B1S2 yellow is B2S2. Based on this I assume wiring is good. Any thoughts?

 

OK, I just want to verify. Bank 1 on a 2003 Toyota Tundra is the divers side of the truck, correct? Just watching this thing graph the voltage output when reving engine B2S3 remains consistent with very little variation. B1S2 fluctuates quite a bit while reving.

 

B1 is driver side, cylinders 1,3,5,7 (from radiator to firewall)
B2 is passenger side, cylinders 2,4,6,8 (from radiator to firewall)

B1S2 is all over the damn place compared to B2S2 or am I just crazy?

Too bad the S2 sensors are different part number for your year, else I'd tell you to flip those two and see what happens. That would help determine if it's wiring or not. Still got the old part?

 

Yes it all over the place. Crazy but seems to me that rules out a harness issue. Is my thinking correct?

 

I don't think it rules out a harness issue. All it shows is - at some points in time - the harness is showing continuity. But if you had corrosion at a connection, a bent pin, or bad ground, you can see similar fluctuations and noise on a line.

I'm not looking at how the harness is actually setup, because I suck at reading the EWDs for these trucks. However, say for example, the upstream/downstream sensor shared a ground. You just replaced the downstream sensor because that's what the code told you was not working correctly. But what if the upstream sensor was actually defective, and backfeeding through ground, making the downstream sensor act a fool?

This is one of a couple reason I'll usually tell people: Your ECU is only as smart as its sensors and logic; it says one sensor on a bank is bad, replace both sensors for that bank. Worst-case-scenario, the other sensor on that bank will die soon anyway, so consider it "proactive maintenance", i.e. you're only busting your knuckles one day, not two.

 

Thanks for the reply shifty. If I monitor S1 on both banks the readings are pretty much identical. Now I know that may not be expected because each bank may have different variables. I gotta admit, S1 looks rather difficult to get out. Sometimes when I am driving I think my exhaust seems kind of loud. Yet I can not find a leak anywhere.