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Discussion Starter · #1 ·
I've got a 2004 Sienna FWD with around 165,000 on it. It's run very well, but I've been throwing some very persistent P0430 codes.

I've done all the "easy stuff" thus far: replaced the gas cap, put in a new PCV valve, checked for exhaust leaks (though I'm not sure it's 100% solid yet) and replaced the Bank 2 Fuel mixture sensor (the one up on top by the radiator) with a Denso identical to OE. I've replaced the front engine mount (by the radiator) and the "Dog-bone" mount/strut to stabilize the engine so it won't vibrate more fissures into the exhaust pipe, leading to more leaks.

What I haven't done: the shroud that should cover the front CAT is gone. I've got a replacement ordered. I hear that the CAT needs to be HOT in order to do its work, so I'll cover it up with an OE shroud (for $45 for a piece of stamped tin) so the CAT will be nice and warm. Waiting for delivery.

I've got a simple Autel 329 OMBII reader. It tells me I've got a P0430 problem as does my dashboard with the check engine lights. Most of the time the reader tells me everything's OK when simple snapshots are taken, but the engine monitor checks all the time and the 430 code comes up every so often.

My questions are two:

1. Where is the O2 sensor for Bank 2 Sensor 2 located? I'm told it's after the CAT which the 0430 code tells me is performing under proper levels. Is that B2S2 located down the flex pipe coming out of the bank 2 side of the engine (the one that's more "forward" on the Sienna)?

2. The difference between my Bank 1 Sensor 2 reading (at idle usually around .600 - .700 V...pretty stable). My Bank 2 S2 reading at idle is often around .600-.700 v but it bounces around sometimes as low as .100v and up to .800 v. What does that indicate?

To avoid replacing the B2 CAT ($1000) I'm hoping there is another option. Maybe the shroud will do the trick. Or is my Bank 2 Sensor 2 O2 sensor bad. But then again, see #1. Where is it?
 

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B2S2 is easy to find. Remove the plastic coverings under the front bumper , lay on your back and look up and you will see it in the piping just after the front cat converter. The wiring is very short , like 6 inches IIRC. It is easy to remove and replace. Denso 2344168.
 

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Discussion Starter · #3 ·
B2S2 is easy to find. Remove the plastic coverings under the front bumper , lay on your back and look up and you will see it in the piping just after the front cat converter. The wiring is very short , like 6 inches IIRC. It is easy to remove and replace. Denso 2344168.
Thank you for that info. I got under the car tonight to reconnoiter the situation. I can indeed get at the O2 sensor (lower bank 2). But as I gripped the pipe leading out of the bottom of the CAT,I noticed that the joint between that pipe and the cat is loose. I can wiggle it. There's play. The cat doesn't move but the pipe does. I'm assuming that would mean a bad o-ring and thus a leak which I hope is leading to these intermittent 0430 readings. I'm going to address the O-ring and we will see then.
 

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I'm going to address the O-ring and we will see then.
Here is my post 6 years ago when I changed out the bank 2 cat converter. The aftermarket gasket I used was Walker part number 31332 from amazon.

UPDATE:" I replaced the bank 2 cat. Converter , in front behind radiator , for the code PO430. I used an aftermarket , Walker brand , number 16392 obtained from Amazon for under $200. .
I renewed the manifold gasket with oem toyota 17173-20030 , $22 . I obtained the flange gasket from Amazon as well , 31332 , under $5. For the job I disconnected and cleaned the battery terminals. The manifold nuts are 14mm and torqued to 36 ft/ lbs. The flange were also 14mm , torque 46ft/lbs. The heat shield bolts are all 10mm. It was difficult to remove the flange studs from the original cat. Conv. So I purchased two new ones from the dealer , , 90116-10149 $4 ,. While at the dealer get a shield bolt as the walker is not fitted with like the oem cat.I found one in my tool box . There is no need to remove the post cat O2 sensor , just the one on top. I cleaned the MAF sensor as well.It took me just about 2hrs for a novice like me. When I buttoned up every thing there was no exhaust leaks and the CEL went away. Time will tell if my fix is successful.
Hope this helps."
 

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Discussion Starter · #5 ·
FINAL (??) UPDATE: I replaced the donut gasget between the flex-pipe and the Bank-2 CAT (front). I cancelled out the CEL codes and it's been code free for some time now. I think I found the problem. I replaced the pre-CAT O2/Fuel mixture sensor unnecessarily, replaced the PCV valve and air cleaner, cleaned the negative terminal on my battery, and replaced the missing shroud on the front CAT, all probably good maintenance, but unnecessary. I paid an auto shop twice to find an exhaust leak. They found one around the Flex patch they installed about 11 months ago and welded the leak, but didn't find the one I found when I simply grabbed the flex pipe just after the Bank 2 CAT and wiggled it. I'm assuming they installed the Donut gasket that now failed when they put in the flex patch.

So, in summary, my problem was exhaust pipe leaks which led to bad O2 readings and thus the message that the CAT was performing blow standards. Thus, the P0430. I'm sure there are other reasons that the P0430 code surfaces, but for me it was exhaust leaks that probably came from a failed flex pipe which came from a bad front engine mount. The mount has been replaced, along with the "dog-bone" strut mount, so I hope this fixes it for some time.
 

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Thanks for reporting back , Regarding the front engine mount, were there any symptoms like a wobbly or jerky engine when moving off. Were there any physical evidences like cracks of fluid leakage?
 
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