P0420- Cat is dead, need a plan of action

You should get a capable scantool and see what codes triggered the "master caution" light (RTOD). Most scantools can't check all systems on a Gen2 Prius. Here's a thread that reviews several scantool apps and devices.

https://priuschat.com/index.php?posts/3290690

Yes, a broken up cat can restrict the exhaust and cause reduced power. That usually only happens if the engine has been misfiring, which sends loads of unburnt air and fuel into the cat- causing it to overheat and fail.

A misfire on a Prius makes a rattle sound as the uneven engine operation "beats up" on the spring loaded damper that connects the ICE to the transmission.

Yes, you have a deficient cat causing a P0420, but without more information and testing, it's just a guess as to what's causing your other problems.

Sometimes guessing works, other times it just costs (wastes) time and money.

Posted via the PriusChat mobile app.

 

If you do buy a new cat I would get one that will clear your check engine light by actually working. This unit does that and fits nicely.



Napa and other autosupplies may have them in stock.

Plus you could join the underworld and sell your oem cat for several hundred dollars. Maybe in Wentzville selling cats is above board like in Texas.

 

I missed the "mid point update" in the first post. If there was a fault that triggered the master caution light (unless it was low engine oil pressure or some-such), then it "should" have set a code that Techstream code read (at least a history code).

I have seldom heard a (broken up) cat rattle when operating the car. I only hear it when smacking the exhaust system at the cat with a hammer or wood block.

You can watch misfire counters in ECM data on Techstream while (someone else) is driving the car. If you see any counters increase while hearing the rattle, that would suggest that you do actually have misfires (most often the result of bad spark plugs and/or ignition coils).

Posted via the PriusChat mobile app.

 

I've used this model in a couple dozen Gen 2s. I also typically install a new downstream O2 sensor (reasonably priced DENSO from RockAuto about $55) The cat was typically costing around $130, but prices have dropped. I bought a couple more just about a month ago.

Catalytic Converter 2004-2006 2007 2008 2009 for Toyota Prius 1.5L Front | eBay

When I first started buying aftermarket cats, I tried several different ones. This is the only model that comes with the correct fasteners and a decent donut gasket. The end of the pipe is necked down to be an extremely good fit over the OEM pipe. Unfortunately, the clamp supplied with the kit fits the "un-necked-down pipe", so I purchase Heavy Duty 1 3/4" clamps from O'Rielly's Auto Parts and they work fantastic.

 

I have used dozens of them and have no problems with codes.

 

I really appreciate the good stuff found on this sight. I just ordered this 75 dollar cat and will get rid of needing to run the 02 sensor extender, the extensor has been working, but my thoughts are that the air fuel mix might be altered enough to cause damage, car has 230k and runs great currently. Bought the car for a thousand bucks, it needed a traction battery and a coolant storage tank to get it up and running and a few cosmetic trinkets over 8k miles later it runs great