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OK, so I'm confused. I have a 2004 Sienna 2WD XLE with a bad cat. My mechanic says it is behind the engine near the firewall. I had already replaced the Bank 2 sensor due to the PO430 error. When the error came back I took it to be checked. I can't find a diagram of how many and where the converters are. I can see the first one facing the radiator and it comes off the manifold. It curves under the engine and appears to curve up toward the firewall and back down again where it connects to what looks like the engine on a German V1 buzz bomb. I'm supposing cat converters all have heat shields? I simply can't find a diagram of where all the converters are? Are there 3?

Thanks for the help???
 

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A few years newer, but basically the same:



 

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Got a chance to look at this in more detail this morning as I too was curious. The exhaust manifold and catalytic converters (front and rear) are integral assemblies and replaced as a unit. They cost around $550 to $700 each. I'm not really sure what is contained in that center pipe. I had assumed that those two bulging units were just resonators, but as this pipe costs a rather lofty $950 to $1000 depending on the parts site, maybe it is a secondary converter? Yet the Sensor 2 (post cat oxygen sensors) are prior to this, so it's output is not monitored. That would be kind of odd, but who knows.... By comparison, the final exhaust pipe / muffler is only $350, and the front crossover (Y) pipe is a mere $250..
 

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Thanks, this really helps. I looked everywhere for a good diagram and just couldn't find it. I even have the Haynes and Toyota Service Repair manual I downloaded. Neither was much help. I had been looking underneath my van from the side and you really can't appreciate where this rests. My mechanic had mentioned it was on the back side of the engine and now it makes more sense. I now have to decide do I try this myself on a gravel driveway with the van on jackstands or pay 120 bucks for the labor. The part is about 500 bucks not including his mark up. Total is around 700 bucks. I was looking around for the OEM part and need to find the part number so this does make it easier to determine what I need. Logic tells me to let the mechanic do it since he has a lift and I'm not as skinny and young as I used to be (although I tell everyone I'm still 29). Thanks for the assist.
 

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Honestly, getting to the backside of that engine to do anything is going to be an experience that you will soon come to regret. Break or strip a manifold bolt back there on a 9 year old vehicle and it's game over. Jackstands on a gravel driveway? Please no.

Are you really sure it needs a cat? Satisfied with the diagnostic work done? Before you go this route, did you consider just changing out the post cat sensor? You'll probably be buying one anyhow to go with that new cat, so why not just try that first?
 

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Yes get a second opinion on the Cat. You may be wasting money. Get a good OBD II scanner and reset the CEL and see if that code continually comes back first.

Toyota cats are very expensive.

Regards, JC.
 

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Ok, I am a little late to this chat but I to have had this question and there seems to be very little clear info on it. I have finally found out the answer to how many cats the second gen sienna's have. They have a total of 3. One cat on each exhaust manifold and one integrated into the middle section between the Y-pipe and resonator. It comes from the factory integrated into the resonator pipe. At the time of me writing this I only found one replacement on ebay at the whopping price of $2400. here's the work around. You can get the resonator pipe by it's self. They make a separate after market cat for that location. Bosal, Magna-flo both make replacement cats for that for about $200-$350. I am replacing everything from the Y-pipe back. New cat, Resonator and muffler section for ruffly $500. That is a far cry better then $2400 for just the one piece cat/resonator pipe. Back to the question of how many Cat's the 04-09 sienna's have? 3. The O2 sensors are located before and after each of the cats on the exhaust manifolds for a total of 4. The third Cat does not have any. Hopefully this info can help some else in the furture.
 
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