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2006 Toyota Sienna CE
I bought this about three weeks ago and no problems other than a DT0430 code popped up a week ago. Haven't done anything about that...

Ok, for the real stumper... I'm coming of a 40 mile trip with a few miles left through city traffic and all of a sudden I feel a slight misfire and notice the speedo needle dropping and the ABS and the Tire pressure light comes on with the check engine light staying on...
This lasted a few seconds and jumped back to normal... That got my attention fast...
Then it happened again about a few minutes later...
Is it a failing computer or a loose connection? I checked for trouble codes and the same old DT0430 was the only one stored...

What the heck? Anybody know what this means? What should I do?
 

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I feel like a 🦃...
I'm going to put this out there and see if anybody can make any sense out of it...
Earlier this morning I reported in the first post about what happened to me. It was strange seeing the Speedo sweeping down and the other lights coming on. and just like that, It went back to normal.

The important thing to remember is the fact that the van was still rolling about 45 mph when all of this happened.

At lunchtime, I ran the engine for the A/C while I ate and no probs...

At quitting time, I stopped by the used car place where I got the van three weeks ago and no probs...

Asked the dealer about the possibility of some starter disable that might be installed for those who have bad credit and misses a payment. Nope he said, there isn't one on that Toyota... Was thinking that I might've had one and it was jamming the computer... Nope scratch that...

Drove the 40 miles home and the engine stalled out in my last turn home and found out how much fun it is to turn the steering wheel without the engine...

Remember in the opening post, I mentioned a DT0430 code? That's the famous catalytic converter code for under-performing...

I didn't think it was that and was going to spend next weekend checking air cleaner, intake manifold for leaks and change the oil.

Was is the operative word, because when it stalled out on me, that was when I realized that's what happened this morning and the torque converter still had enough viscous movement to enable the engine to be turned over by the transmission... Like the old PowerGlide transmissions used in the classic muscle cars of yesterday... When it happened the second time this morning, it stalled out but the transmission kept the engine spinning and restarted.

This has to be the answer, the dash lights came on because the engine stalled and went out when the tranny restarted it... Twice... And when it stalled out near home, I was going too slow for the old tranny restart trick and she stayed stalled...

What happened is that Catalytic Converter Bank 2 is plugged up and failing, thus the DT0430 code and I upgraded my OBD2 with the 10 dollar plugin for my van and now I have access to further diagnostics... I can read Mode $06 information and lo and behold, it IS the bank 2 cat...

Check out the screenshot and notice Component Id $02 - TId $01 - Manufacturer defined. That is the bank 2 cat and it is failing badly...
45794

Now we all know what happened to me and now, with a groan, I gotta buy the whole dang thing and it has to be OEM because I don't want the computer getting picky about non OEM stuff.
Fortunately there isn't too many bolts and it's right there between the engine and the radiator...

Whee! isn't this fun!!! NOT!
 

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Agree. It's the sensors (oxygen below, wideband A/F above) that the ECU is extra picky about. As long as the aftermarket cat has sufficient precious metal in it to do the job, it should get you a few good years and be much easier on the wallet.

But.... Why did one cat fail? No indication of an accompanying P0420 (rear bank). When you get it back together, keep an eye on fuel trims to see if you aren't overloading that front cat and killing it.
 

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Discussion Starter #7
Fibber2 here is a print out of the last report from the OBD2... Strangely the Bank 2 Cat is well back within range, while as in post above it was way out of range at 191... So the idea is something is causing the fuel trims to get out of whack, thus over loading the Bank 2 Cat?

I have attached images of a html report to this post, can you look (if you have time) and tell me what it reveals to you? I do see that the Bank 2 Cat is now operating within spec when before it wasn't... I also notice the short term fuel trim numbers are wildly different from Bank to Bank in Mode $02-Freeze Frame... Still haven't grasped the significance though...

Thank you Fibber2, your help is greatly appreciated. :giggle:
45807
45808
45809
45810
45811
 

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I wouldn't think that a plugged cat would make the van stall, especially intermittently. You still have the other three cylinders running.
 

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Perhaps that upstream o2 sensor is "acting" up if that's possible. This says at least the converter might be okay.
I know, right? I think Fibber may be on to something with the idea that the Cat got overloaded.

I still need to learn how and what makes the calls for the fuel trim, which I think it means the amount of fuel to be distributed via the injectors.
It probably governs pressure and length of time injector is open or operating...
It might even be connected to the fuel pressure pump and whether the charcoal cannister got drowned by excess fuel in tank (topping off)...
Right now, in my mind, until I get an understanding of the fuel trim and it's intricacies, I'm just flailing around like a drowning man grasping at many theories that could be ridiculously without merit.

I think I'm going to see what Google has to offer in 'Toyota fuel trim'...
 

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Discussion Starter #11
I wouldn't think that a plugged cat would make the van stall, especially intermittently. You still have the other three cylinders running.
Maybe it isn't plugged?
What if overloading it (too much unburnt fuel) causes the cat to choke?

In the screenshot in post #4, that cat failed and the next day, in the Diagnostic Report in Post #7 it passed. the Bank 2 Cat is listed as Component $02 in Mode $06-On Board Monitoring in both reports.

On the day the stall occurred, that cat was the only thing that was reported as failing, but on the next day, it passed the monitoring with comparable numbers as the other cat... In fact, everything passed the monitoring...

What happened? Now that is the $64,000 question...

I think that now it's obvious that this cat choked one day and the next day it didn't.
Ergo, something is making it choke because if the cat itself was plugged, it would fail all of the time, right?

This is why I think Fibber may be on to something, he mentioned a scenario where the cat can be made to choke and I myself have seen this cat choke and then unblock itself...

This is fun playing detective and know this...
Finding all of the clues spells the difference between solving the case or letting it get worse to the point where it won't run, as evidenced by the irregular stalling...

Betcha something's wrong with whatever makes the call for the fuel trim...

Yours truly...
 

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There are many things that affect the fuel trims, a few are vacuum leaks, the maf sensor can really wreck havoc if it's not right. That would affect both banks though, the o2 sensor maybe.
In the case of a vacuum leak the ecu uses info from the maf and o2 sensors to determine how much fuel to add. If there is extra unmetered air entering without the maf seeing it the o2 sensor will sense a lean condition and add more fuel than normal. This would be noticable on the fuel trims. You might have to be able to record live data to see this. A snapshot might not be enough.
That short term trim shown above is interesting, one bank shows 2.34 and the other shows -5.47.
 

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There are many things that affect the fuel trims, a few are vacuum leaks, the maf sensor can really wreck havoc if it's not right. That would affect both banks though, the o2 sensor maybe.
In the case of a vacuum leak the ecu uses info from the maf and o2 sensors to determine how much fuel to add. If there is extra unmetered air entering without the maf seeing it the o2 sensor will sense a lean condition and add more fuel than normal. This would be noticeable on the fuel trims. You might have to be able to record live data to see this. A snapshot might not be enough.
That short term trim shown above is interesting, one bank shows 2.34 and the other shows -5.47.
Yeah, that's the one I'm focused on right now... the -5.47 means the O2 sensors are telling the computer that bank is too rich and the fuel trim is being subdued or subtracting the amount of fuel to make it right.

Sticky or leaking injector? No injector codes though...

I remember when I built my first engine, it was a 351 Cleveland with Holly 750 and mild to moderate split lobe cam... When I first started the engine, I ran it through initial break-in and shut it off. Later on in the evening, the machine shop guys who did the machining work came over to admire my work and I remember it was getting dark...

I started the engine and let it idle, I was loving the loping sound from the exhaust and as the engine warmed up I noticed that the headers were turning cherry red. That got my attention fast and I pointed it out to my machine shop friends and they said that means it's running too rich.

Having said all of that, it seems to me that if Bank 2 is running rich, then it should be glowing red at least a little, even with the fuel trim in the negative range...

I'm going to make a run to the store and back then pop the hood and take a look...

Back in a bit. Don't worry, where I live doesn't have a curfew or shelter in place order... The next county over does though... Damn the WuFlu...
 

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Surprise! My county does have a shelter in place order! I think I will wait till morning when it's still dark...
 

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Things are getting strange indeed, seems like some of these normal problems play second fiddle to the current events, stay safe,,
not sure on this but I always thought lean running engines ran hotter.
 

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Things are getting strange indeed, seems like some of these normal problems play second fiddle to the current events, stay safe,,
not sure on this but I always thought lean running engines ran hotter.
Well, they generally do, but in my 351C the fuel was still burning past the exhaust valves right into my headers... That's pretty rich...
When the pipes start glowing, that means not all of the combustion is completed in the cylinder and is still burning as it passes out into the exhaust... Engine does run cooler because some of the heat is generated outside of the engine... Of course exhaust lobe centerline timing plays an important part in this by staying open longer for increased scavenging of the cylinder...

Oh yeah, in my diesel, it's a non turbo IDI and when you play around with the fuel adjustment screw or install a turbo, it is heavily recommended that a pyrometer is installed right next to the exhaust port so you can monitor exhaust temps because pistons are aluminum and they melt at 1800F. As long as the exhaust temps don't go past 1650F you are good to go but the manifolds are just starting to turn a dark red that you can't see except at nighttime...

KWIM?
 

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Dang it! The sun is up and can't see if the exhaust manifold is red after a drive...
Will do it this evening.
Will drive around a little and generate some more reports...
I sure miss eating out for Sunday breakfast...
Damn WuFlu...
 

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Didn't get the chance to check for exhaust manifold heating up to a red color indicating extreme rich fuel trim.
Instead when I get home from work, I will perform some vacuum testing...
That will point me in the right direction, as far as replacing the cat.
After the replacement, as Fibber said, I need to watch fuel trim and see if it doesn't vary much from 0. Actually he just said to watch the fuel trim, I added the obvious...
If I still have Bank 2 short term negative readings, then I need to look for a leaking injector, I think...
This sure is different than old school wrenching like as with the 351C or IDI International Diesel engine... I hate electronics because more problems manifest that require repair compared to just carbureted engines. Heck even my diesel was more dependable because it used MECHANICAL injectors... Easy peasy...
 

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Are you certain it will glow red, there are a lot potential variations here.
How thick the steel is, how fast or slow it dissipate heat etc. Might not be the same
Conditions as before with other vehicles. It if is glowing I would think you could see
It a bit in the daytime . How is the fuel mileage?
 
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