The quietest file in the whole range — but the two loudest complaints in it are $9,000 transmissions.

The 2020 has the third-generation sliding-door mechanism unchanged, and it fails the same way: the cable that pulls the door snaps and hangs down above the rear tyre, the centre hinge corrodes and jams the door as it closes, and the lock assemblies seize. Toyota's class-action settlement paid for those parts on 2011–2018 vans through the Customer Confidence Program ZKI and Warranty Enhancement Programs ZH4 and ZH5 — ten years and nine-plus-one years from the van's first day in service, no mileage cap. It stops at 2018. A 2020 owner in the federal file makes the case bluntly: their door cable snapped, disabling the door, and they note that the bulletin behind the earlier programs was published in June 2019, before their van was built, and that Toyota 'did not change the mechanism until the 2021 model redesign'. Their other observation is worth taking on board as a buyer: with the cable broken, disabling the power door system did not let the door open manually — they had to cut the cable with wire cutters to free it. Cycle every door repeatedly, and treat any hesitation as a cost you will carry.

A genuine theme in this year's small file, and an expensive one to chase. One owner parked on a downhill slope in heavy rain and found water coming out of the passenger-side seat belt, with the trim above the window stained down to the airbag area; the dealer wanted $1,000 to $2,700 simply to remove the headliner and try to find the source, and advised not parking nose-down when rain was forecast. Another reports a leaking or clogged sunroof drain causing extensive interior damage. Our mechanic source's warning about headliner water damage on this van family is that the repair cost is out of proportion to the van's value. On any 2020 you look at, press the headliner near the corners for damp, pull up the carpet edges, sniff for mildew, and look for tide marks around the seat-belt anchors.

The one Toyota safety recall on this year, and it matters. The low-pressure fuel pump inside the tank can fail, and Toyota's own summary is unambiguous: 'if the fuel pump fails, the engine can stall while driving.' The campaign explicitly names 2017–2020 Sienna and dealers fit an improved pump free (Toyota code 20TA02). The 2020 complaint file shows the ragged edges of that campaign: owners waiting many months for parts, including a university fleet that parked its van for six months; one owner whose pump was replaced under the recall and whose van stalled again a year later; and — the one to note if you are buying — an owner whose independent mechanic diagnosed a failed low-pressure fuel pump on a van whose VIN was not included in the recall at all. A federal court approved a settlement in December 2022 requiring a Customer Support Program for certain 2014–2020 vehicles repaired under this recall; the terms are not stated in the bulletin summary, so verify them in the bulletin PDF.

Toyota has an open bulletin for an oil leak from the No. 2 oil pan on 2017–2020 Sienna and 2017–2022 Highlander, narrowed in a later revision to engines whose serial number begins with F or G. Toyota listed it as 'currently under investigation' and asked technicians to photograph the leak before repairing it. Our mechanic source adds the water pump, which he says still leaks on the updated V6. Separately, this year's file carries a striking parts story that is worth knowing before you buy any van this age: a driver's door mirror came loose from its housing, could not be repaired only replaced, was quoted at $1,937.70 and $2,025.29 by two different dealers, and then sat on national backorder for more than a year while the owner's van could not pass inspection. Also present: an ABS wheel-speed sensor short with a fractured brake actuator at 28,000 miles, a driver's front axle assembly found coming apart internally during its first service, and a rear tail-light-side wiring harness fault that took out the pre-collision, lane-assist and airbag warning lights at 60,000 miles with the harness on backorder.

Our mechanic source treats front struts as a running cost on this van — 'almost every other one I get in the shop' has leaking front struts — and names the cause: water off the windscreen collects in the cowl and rots the strut mount from above. He also flags front lower control-arm bushings, testable by braking hard at low speed with a light hand on the wheel; a sharp jump to one side means they are worn. Brake pad life on a loaded van he puts at 25,000 to 45,000 miles. If the van is all-wheel drive there is no spare wheel under the floor, so it runs on run-flat tyres: he says expect uneven wear and replacement around 30,000 miles, while a long-term owner of a comparable van reports roughly 10,000 miles per set at about $1,000 a set. Both figures are published because both were given. The all-wheel-drive system itself he calls 'a great system', with one cheap wear item — a mount at the front of the rear differential that fails and produces a loud clunk from the back under hard acceleration. Toyota has a bulletin for noise from that same rear-differential coupling on 2014–2021 vans.