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Discussion Starter #1
I recently found and replaced the O2 sensor on bank 1 sensor 2. The location is probably the closest plug with the shortest pigtail closest to the front jack point in case anyone wants to know.

After replacing the O2 sensor, tightened it, plugged the new sensor in, & clearing the code with the Torque app, the light came back on again after a day or so.

Possible wiring? Is my cat going out?

My '12 Highlander has 130,000 miles for reference.
 

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Bank 1 means the front bank that is facing the front of the car?

Sensor 2 means after the catalytic converter?
 

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What is/was the code that you're getting? A bunch of things can cause the CEL. a loose seal at the gas cap, bad or dirty maf sensor, bad or dirty injectors, air leak causing unmetered air to enter the intake causing a lean condition and the computer can't compensate, and like you mentioned the cat could also be the culprit.
 

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B1S2 would be the post cat sensor on the bank containing #1 cyl. Or the only post cat if only single exhaust at that point.

It's main purpose is to monitor how well the cat is working, not to control AFR. That's done based on the S1 sensors.

But as asked above ....what's the code?
 

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Discussion Starter #5
The fault code is P0037 which is the issue indicated as above but it says it could be the wiring as well?

And yes, I replaced the O2 sensor after the cat.
 

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The fault code is P0037 which is the issue indicated as above but it says it could be the wiring as well?
We really are trying to help you, not give you a hard time. But we have to speak the same language, even if one or both of us has a "strong accent".

You say that you indicated P0037 "above". I can't find it. And you haven't told us which engine.

You describe the location in reference to a jack point. Even if I had a Highlander in my D'way, I would not be inclined to go out and crawl under it to locate the sensor you are talking about. Reference points/relative locations on the exhaust system are much more helpful. And understanding of the definitions of bank# and sensor#, as spec'd by the OBD-II standards, helps as well. Using those, one doesn't even need to know whether the engine is transverse mounted (or not), because the standard uses #1 cylinder (car manufacturer defsignated) as the reference point. Not front, rear, left, right.

You say you found the O2 sensor issue. What was the issue? Note that some codes can come and go under varying conditions, particularly P0420, which can indicate a CatCon that no longer works well enough. That's the code usually set when the converter actually needs replacement.

Note that some codes, including, I believe, P0420, are two trip codes that don't set the first time. So, perhaps it's not that the problem was gone after you replaced the sensor and cleared the codes...it was just "pending" until repeated.

Did you put in a Denso brand sensor, purchased other than ebay or Amazon? Too many faux sensors sold those places.

Give us some more info and we'll keep tryin' to help.
 

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AvConsult
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P0037 is an O2 sensor heater circuit fault. Wiring issue (open), connector or pin fitment issue at sensor or PCM. Possibly PCM itself, but I'd rule out everything else first. Likely NOT upstream 12v power issue, as that power buss is shared by lots of things that PCM would probably notice as failing and set additional codes.
 
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Discussion Starter #9
We really are trying to help you, not give you a hard time. But we have to speak the same language, even if one or both of us has a "strong accent".

You say that you indicated P0037 "above". I can't find it. And you haven't told us which engine.

You describe the location in reference to a jack point. Even if I had a Highlander in my D'way, I would not be inclined to go out and crawl under it to locate the sensor you are talking about. Reference points/relative locations on the exhaust system are much more helpful. And understanding of the definitions of bank# and sensor#, as spec'd by the OBD-II standards, helps as well. Using those, one doesn't even need to know whether the engine is transverse mounted (or not), because the standard uses #1 cylinder (car manufacturer defsignated) as the reference point. Not front, rear, left, right.

You say you found the O2 sensor issue. What was the issue? Note that some codes can come and go under varying conditions, particularly P0420, which can indicate a CatCon that no longer works well enough. That's the code usually set when the converter actually needs replacement.

Note that some codes, including, I believe, P0420, are two trip codes that don't set the first time. So, perhaps it's not that the problem was gone after you replaced the sensor and cleared the codes...it was just "pending" until repeated.

Did you put in a Denso brand sensor, purchased other than ebay or Amazon? Too many faux sensors sold those places.
Oh no I didn't take it that way :) I just assumed it was the O2 sensor as that was the first thing that was hinted.

P0037 according to Torque's link says it's the downstream O2 which it took me a couple tries to figure out. It's closer to the engine side of my V6 (assuming there are four O2 sensors) whereas the other O2 sensor behind the cat is more towards the oil drain plug area.

I bought a Bosch from Amazon...you know, thinking I can save some money...

Thanks. I'll have to check the ground as well as much as I try to keep at least the negative terminals clean, it is an aging area for wires & contacts. I just hope it's something like a broken wire I have to trace :\

P0037 is an O2 sensor heater circuit fault. Wiring issue (open), connector or pin fitment issue at sensor or PCM. Possibly PCM itself, but I'd rule out everything else first. Likely NOT upstream 12v power issue, as that power buss is shared by lots of things that PCM would probably notice as failing and set additional codes.
Thanks, will do :)
 

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Lets just make sure some fundamentals are right.

Bank 1 means the bank containing #1 cylinder. From everything I can see, on any transverse mounted V-6 TOYOTA engine, the bank closer to the firewall contains cyl #1.

Sensor 2 will be the second sensor in that bank, with the count starting at the engine head. It should also be the last (closest to tailpipe) sensor in that bank.

Does the sensor you swapped meet that description of location?

What codes did you start with? What codes do you have now?
 

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AvConsult
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TedL has a point; make sure you replaced the correct sensor. And if correct, that the replacement sensor wasn't BWB - Broken When Bought.
 

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If Bank 1 is for the bank that has cyl #1 and TedL says that would be the bank closer to the firewall, then the wrong O2 sensor was replaced.

Who makes the O2 sensor for Toyota. Denso?
 

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Yes, every original O2 sensor I've ever pulled from a Toy has been Denso.
 

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AvConsult
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For 2008 V6 HL:

309846
 
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