oxygen sensor question.

[bigskyeric]

Hi everyone.. I haven't been on here in a while, which is a good thing because it means my 04 4runner with 209,000 miles hasn't had any issues.

I know the oxygen sensor questions come up often and a few that I read said to check the 'sticky'... but there isn't a sticky (unless I'm blind)

Anyway... here are my questions.

My T4R is throwing a P420 catalyst below threshold code. It deosn't specify which bank it is. I'm using the iPhone app 'engine link' which has been awesome so far.

Most threads I've read say that it is most likely NOT the cat but the sensor 2 oxygen sensors. Both sensors were replaced last year and I used Denso sensors. Engine link is reading both sensors as running between 0.2 to 0.9 voltage. Bank 1 sensor 2 averages about 0.1 lower voltage than bank 2 but I figure this is due to it's distance being further away from the engine.
Both Bank 1 sensor 1 and bank 2 sensor 1 are not reading anything and appear to be dead. So I figured this is the culprit. But from my research, sensor 1 has nothing to do with reading the cats because they're before the cat.

To make this even more confusing, what I thought was the oxgen sensors (bank 1 and 2 sensor 1) appears to be the air/fuel mixture sensor according to this diagram. http://www.toyota-4runner.org/maintenance-detailing/52109-h02-sensor-bank-1-sensor-2-p0136-code.html (leaving me unable to find the oxygen sensors)

But then this diagram says otherwise. http://www.tundrasolutions.com/forums/attachment.php?attachmentid=43743&d=1247837544

Anyone know which diagram is telling the truth?

I know the easy answer is... replace the sensors since they're obviously dead. But at $100 a piece (even at Rockauto.com) for the denso.......

Thanks in advance for any insight you may have.

-Eric

 

[Ralph Blake]

Has the gas milage dropped? If not why spend the money? I hVe a car that for the last 11 years has had a check engine light. Code says cat O2 sensors,gas milage never dropped. Still going strong.

 

[4RunnerJosh]

The sensors before the cats are air/fuel ratio sensors and the ones after the cat are the 02 sensor they work together to tell the ecu if it needs to lean out the fuel or make it more rich. If the code is saying cat. Below efficiency then your cats are worn out and not pulling any toxins out of the exhaust which will cause the ecu to make it run rich.

 

[radlynx]

is that a v6 or v8? at that mileage, replacing the cat is the way to go.

 

[paperchasin]

There isn't a "bank" for P0420 because it is simply telling you that your catalyst is no longer functioning as efficient as it should and you only have the 1 catalyst. At 200K miles, assuming you've never replaced your cat previously, and the fact that you've already replaced your sensors recently, I'm betting that you simply do need a new catalytic converter.

To answer your question about the sensor readings, the fact that your sensor 2 readings are following your sensor 1 readings confirms that your cat is indeed needing to be replaced. With a good catalyst, your sensor 2 should read fairly steady and does not follow the sensor 1 readings.

 

[BlackWorksInc]

There isn't a "bank" for P0420 because it is simply telling you that your catalyst is no longer functioning as efficient as it should and you only have the 1 catalyst. At 200K miles, assuming you've never replaced your cat previously, and the fact that you've already replaced your sensors recently, I'm betting that you simply do need a new catalytic converter.

To answer your question about the sensor readings, the fact that your sensor 2 readings are following your sensor 1 readings confirms that your cat is indeed needing to be replaced. With a good catalyst, your sensor 2 should read fairly steady and does not follow the sensor 1 readings.

One thing I'd like to point out is that a P0420 is a Bank 1 Catalyst Inefficiency DTC. P0430 dictates a Bank 2 failure.

Everything else is accurate though. It does sound like you catalyst has failed.

If you want read up a little bit on diagnostic procedures/ways to approach the problem I mention it in the Toolbox thread.

http://www.toyota-4runner.org/4th-gen-t4rs/132953-toolbox-how-use.html#post1272379

 

[bigskyeric]

One thing I'd like to point out is that a P0420 is a Bank 1 Catalyst Inefficiency DTC. P0430 dictates a Bank 2 failure.

Everything else is accurate though. It does sound like you catalyst has failed.

If you want read up a little bit on diagnostic procedures/ways to approach the problem I mention it in the Toolbox thread.

http://www.toyota-4runner.org/4th-gen-t4rs/132953-toolbox-how-use.html#post1272379

Thanks for the info... what about both upstream sensors ? they're both dead according to my readout,and where are they?

 

[bigskyeric]

Has the gas milage dropped? If not why spend the money? I hVe a car that for the last 11 years has had a check engine light. Code says cat O2 sensors,gas milage never dropped. Still going strong.

My ABS/stability system is turned off because of the code. I sorta kinda need it up here in northern minnesota.

 

[CAN-03runner]

Maybe I read too quickly but I didn't see if it's a V8 or V6 . On the V8 the cat is part of the exhaust manifolds. It makes it and even more expensive part and labour intensive. Don't know if it's also the case with the V6.

before you put in at least 1000$ into this, replace the exhaust seals at the pipe joints at least the ones at the cat. This worked for me twice. First time I used a Toyota part for the seal, worked a few years until it deteriorated again. Then it came back. I used a non Toyota seal, lasted a year, then I changed my exhaust manifold with built in cat...V8..I also had a cracked manifold and the ticking was driving me nuts.... so new cat new seal still had low efficiency code. Replaced the seal with a Toyota part instead of the muffler shop special and the code stayed away...actually I'm not even sure the shop that did the work even put a seal and/or I wouldn't be surprised they didn't reuse the same old seal.

My code is back. But I can see and smell exhaust around where the seal/joint of the cat is. Time for a new seal again.

Basically what I'm saying is, the seal is something like 2$. Change it first . During the cat replacement the seal should be changed....but you won't really know what was the culprit, 2$ seal or 1000$ cat.

 

[CAN-03runner]

My ABS/stability system is turned off because of the code. I sorta kinda need it up here in northern minnesota.

I'm not 100% sure the abs is off. In my testing I'm pretty it works I think it would actually be illegal to turn it off. But as a scare tactic to get your car to be checked out, it works. Test it. Find a safe place to try and lock up the brakes and see if they pulsate .

As for vsc....that is turned off....well sort of again. I actually think that it is in fact delayed. With the same codes active, I tested a left turn I always take to the highway in the winter and there is always a snow and ice build up. If I give too much gas the vsc steps in and beeps at me. With the codes active, I tested. I was able to have the truck get pretty loose, and slide substantially more before the beeping started. But..I'm not confident in that. Not sure if vsc actually still did it's thing , in a very delayed way, or it was just beeps indicating I was sliding out, but vsc didn't actually do anything.

 

[bigskyeric]

I'm not 100% sure the abs is off. In my testing I'm pretty it works I think it would actually be illegal to turn it off. But as a scare tactic to get your car to be checked out, it works. Test it. Find a safe place to try and lock up the brakes and see if they pulsate .

As for vsc....that is turned off....well sort of again. I actually think that it is in fact delayed. With the same codes active, I tested a left turn I always take to the highway in the winter and there is always a snow and ice build up. If I give too much gas the vsc steps in and beeps at me. With the codes active, I tested. I was able to have the truck get pretty loose, and slide substantially more before the beeping started. But..I'm not confident in that. Not sure if vsc actually still did it's thing , in a very delayed way, or it was just beeps indicating I was sliding out, but vsc didn't actually do anything.

It's a V6 and I was actually thinking the same thing about the seals. Last winter when it dropped down to -20 degrees i could hear a ticking sound coming from the exhaust. I didn't look to closely but I'd bet it was at the cat. I haven't tested the ABS but I did check the VSC on a dirt road and it didn't kick in. I'll buy a new seal tomorrow and see if it does the trick. Thanks for the info!