Hi folks,

I think I have had a cat converter failure on my 2012 4Runner. It happened all of a sudden when I was on the highway doing about 110 kph. It sounded like there was heavy rain on the roof initially, and then later when I slowed down and rolled down my window it sounded like a bunch of rocks in a metal can were strapped under the truck rattling around. When I corner at relatively slow speed, the rattling moves side to side.

My guess is the cat converter failed. Anyone have any experience with this?

I will take it in to a garage tomorrow for an assessment, but if anyone has any ideas I would be happy to hear them. Obviously, the cost of replacing one of these is not making me happy!

Thanks

When they fail, they get stuffed up. Have never heard of the innards coming loose.

the innards can come loose, and if its bad it can make a rattling sound, but failed cats usually also come with noticeable reduced performance and a check engine light

could the sound have been a heat shield rattle? it's not uncommon for them to fall and rattle against the exhaust

(could also be a muffler)

Either of those were my initial thought, especially in the absence of any other symptoms. The sound initially seemed almost aerodynamic, like something was stuck under, but over time (like 10-15 mins), it seemed to be more like a rattle than just a vibration.

I am puzzled as I am pulling no codes, and I agree also that these things typically give you other signs. Plus, it should not fail at all normally. I wondered if a sharp stone may have penetrated the cat as we were on gravel roads, but even that seems odd.

The innards are basically a honeycomb kind of metal piece. It can corrode and break into pieces. But yes, it does seem that there are prior symptoms before that will happen.

the cat doesnt disintegrate that easily. Either rocks in your heatshield rattling aroud or skid plates.. or just some kids in the neighborhood that decided to throw rocks into your exhaust pipe

What you suggest is logical. I will have to crawl under there and see if I can figure it out.

Thanks!

Thanks everyone for your help. I don't have much to contribute on this forum, but I am grateful that others have knowledge to pass along.

I got under the truck and pulled and prodded a bunch of bits and it turns out a heat shield was loose. The bolt and nut had basically worn away the hole and it was just hanging there. If I could lift it I could probably rivet the thing up myself, but as I don't I will have to find someone to reattach it.

Thanks again, folks!

Attached Images