That usually is the air fuel ratio oxygen sensor. Common problem over time on a lot of vehicles.
The 1st gen Tundras were hard on O2 sensors but in the big scheme of things no worse than most.
Did see one article that mentioned that the ECM threw that code when a shift solenoid in the A/T failed.
Not a common response for that code and considering he mentioned a bad smell, that would also lend itself to the O2 sensor.

 

Thanks, sdspeed! I am now wondering. The dealership called and said that we were lucky that the foam didn't dump into the pumps and ruin the pumps so they are just replacing the 2 secondary injection valves. I hope that sounds right considering the smell coming from the exhaust.

 

The Tundra and Sequoias had Secondary Air Pumps that are related to the Emissions system and they are known for being junk. Not sure what foam they're talking about unless it's from the Evaporator Canisters or if an additive like Sea-foam was bing used. Doesn't matter as long as they find it and ya don't have to get a second mortgage to fix it.
A P0410 code is normally what will be seen on a SAP but maybe the O2 sensor caught the fuel mixture being to far out of parameters to adjust so it threw the P2240.

 

If you're concerned about whether this $1300 repair will actually fix the problem, you could get a second opinion either from another dealer or from an independent shop that specializes in Toyotas. Most independent shops treat you better than the dealerships because they know they're not the only game in town.

 

Update: We ended up calling our local mechanic we have used for years and letting him know the same information and he said the dealership was fixing it for about $500 more t han what he would charge us. By the time we took the day off work, drove the 4 hours each way with a rented car trailer to tow it back here then had him repair it for 1 day then took another day off work to drive t he truck and another car back down to the college the 4 hours each way, we would probably be in the hole. ha! So we let the dealership repair it. He said the same thing as you, SDSpeed in regards to the foam. He said the only thing he could figure was the guy was talking about a possible PIECE of foam ( I had the idea of liquid/air foam) and even then, the motor has that happen a lot and rarely does it destroy anything so he was calling "bananas" on the dealer for that. It turns out he has had several of his customers use that dealership for their kids in college and they tend to be fairly honest and do the work pretty close to what a regular mechanic /non dealer would charge so he said the truck was in good hands. He also said the exhaust smell was probably due to the age of the truck/90k miles and he had just had it in his shop in January for the 90 k mile checkup and saw no hint of exhaust issues. Thanks everyone for allaying my fears and keeping me from offering up my first born for payment.

 

Glad to hear ya got it resolved. It's now the dealers problem.

 

LOL! I hope it is no one's problem. I have to cover this truck for another 4 months til the kid graduates college then HE is hoping he brings home his first baby from the hospital (whenever he finds the woman of his dreams???) in this truck at some stage in his life. He is 22 and has had it since he was 16 and he absolutely loves this truck. LOL! He gets angry when his dad drives it because his dad is notoriously hard on vehciles. LOL!

 

Finding the "right" woman is kinda a big deal.
Compared to when I was 22, trucks are chick magnets now..LOL

 

Truth! The one he has now, is fairly new, but she is one we really like...she also drives a brand new Rav 4 and loves it. Cracks us up because he LOATHES riding with us in our 2010 Rav 4 or our 2017 Highlander because he claims they are ugly. He also doesn't like Dad's 2019 Tundra either so there is also that. LOL! She loves his truck because it is normally clean.

 

LOL ...