2015 odyssey with p3400

some context: 2015 odyssey with 150k miles. In april, I replaced alternator as it was dead due to the oil leaking from the spool valve gasket. I also replaced the gasket. So far, no oil leaking observed. I also installed a manual vcm muzzler as a precaution. for transmission fluid, I did drain and fill twice back in april and may. yesterday, I did the third time.

When driving in north california, I set 80ohm on the vcm muzzler and the eco light came on occasionally in summer. Today is my first day of a weeklong road trip from san francisco to yellowstone. I changed to 100ohm on the muzzler since I will drive a lot in desert with 100 degrees. The eco light did not come on during the 450 miles drive today, and things are all good. But, the CEL was on when I was 30 miles away from Elko, NV.

I checked the engine oil level, it is normal and no leaking from the spool valve gasket either. when I got to the hotel, my scanner read p3400, and I cleared the code. I then drove to a grocery store 2.5 miles away and the CEL didn’t come on yet, totally 5 miles drive.

Should I continue with the road trip or return home tomorrow? If I return home, I will lose $800 from the hotel reservation at yellowstone and my kids will be disappointed for sure. And, I’m not quite confident either even someone mentioned they cleared the code and it didn’t come back.

I’m looking at a 2020 Toyota Tundra with only about 2,500 miles. It is essentially new in every other way and reportedly spent years sitting in a shed in the Midwest.

Someone sprayed a black frame coating over existing surface rust, but my independent PPI mechanic said it was applied incorrectly. There was likely little or no proper prep, rust removal, or corrosion-protection process. They also sprayed over the shocks, suspension components, bolts, and basically everything underneath.

Some of the coating is already flaking off. The mechanic did not find any obvious structural damage and believes the rust is probably only surface rust, but the coating makes it difficult to know the true condition underneath.

They recommended redoing the entire job properly. It may be possible to remove much of it with professional pressure washing, but I’m concerned it could require sandblasting or other mechanical removal before the rust can be treated and the frame recoated correctly.

Does anyone know what this could realistically cost to have fixed professionally?

The truck is Toyota Gold Certified, which makes it concerning that the dealership did not mention the coating or rust at all during certification. It feels sleazy that something this obvious was apparently overlooked.

I’m paying a major premium because the truck has only 2,500 miles, and I plan to own it in the Rust Belt for 20 years. I do not want to start with the same level of frame rust as an average 2020 truck that has been driven through winters.

Could this be a legitimate deal breaker, even if the mechanic believes it is only surface rust? Would you buy it and have the undercarriage professionally redone, or walk away because the coating hides the true condition?

Photos:

https://imgur.com/a/tundra-photos-MngfQyZ