I just picked up the above vehicle, automatic trans, quick scan OBD2 shows clear, with 122k miles on it from a guy in Los Angeles, (I'm in Reno Nevada).  Some features weren't working on the back hatch  (wiper, squirter, defroster, keyway wouldn't turn) and figured I would just fix those as I was getting a pretty good deal ($16k) on a $60k vehicle.

I first went to a locksmith to get the keyway unstuck, and when he popped the interior cover, I could see all the rust "chunks" in the inside of the hatch, and some fell out.  One about the size of a dime, and half weight of a penny. The chunks had stopped up the drain holes in the corners of the hatch, and through the years, mud had collected in the corners of the hatch. I filled the bottom 20% of a qt freezer bag with rust and mud of what I scraped, and vacuumed out.  Of course I doused the whole interior of the hatch with WD40

When I was first purchasing the vehicle, the seller did roll the back hatch window down, but had trouble rolling it back up.  Small wonder.  Upon further investigation, this vehicle was subjected to salt damage, the window regulator was what was creating all the rust chunks.  And upon further investigation, found out the vehicle was originally purchased in Wisconsin!  (road salts) 

Fun Fact;

WisDOT uses an average of 526,000 tons of salt and 14,000 tons of sand per season statewide. The total storage capacity of salt for use on state maintained highways is about 562,000 tons. ... However, it only takes about 30 vehicles traveling at highway speeds to blow the sand off the roadway.

A great local Locksmith says he was expecting pin springs (spring steel) to be corroded out, but it turns out pins were good, springs were good, pot metal key barrel was "expanded"  30 minutes later, the key worked. Funny to see that it's merely an electrical switch, with no mechanical connection to anything  🙂

Now that I knew what was suspect, I started noticing the rust intrusion;  bottom driver door hinge showing signs of rust, but top hinge ok, front lower corner of driver door showing signs of rust through paint, spare tire rust dots, hatch keyway stuck, rear hatch regulator rotted out, etc.

The vehicle is low to the ground and I haven't taken a close look underneath.  I did notice the spare tire metal rim has small bubbling rust dots all around the rim.

I called the dealer and gave them the VIN to get a history of recalls and repairs (TY Toyota for being detail oriented and info accessible)

I had three recalls in mind, but they only copped to two;

• master window switch replace (completed on mine)

• add plastic shim to accelerator pedal (completed on mine)

Using Wiki for the Sequoia, they mention;

• a "within 12 year of purchase" recall for frame rusting issues.  10mm hole =replace frame, less than 10mm spot rusting = undercarriage treatment applied 

The Toyota service supervisor made no mention of the "frame rust recall"  I asked specifically about it, but he said he found nothing about it for my vehicle.  I wonder if Toyota just deletes that info since the vehicle is out of the 12 year time span?

I'm putting the vehicle in the shop this Monday to have the related items repaired and/or replaced.  I'm going to ask them to assess the rust problem, for the frame specifically, and give the rest of the vehicle a once over, plus a deep scan of OBD2.

My questions; 

•  Is there something "corrosion related" I should pay special attention to going forward since I intend to have this vehicle for the next 30 years, like I had my last Toyota for that long? 

•  Is there something I can do now, to mitigate a frame rusting issue going forward?

Thanks!