A brand-new hybrid-only Sienna built entirely from proven parts — with one brake behaviour Toyota still hasn't fully cured.

Toyota's wording: 'A short circuit may develop in the Occupant Classification System (OCS) sensor, preventing the front passenger air bag from deploying.' The Occupant Classification System is the sensor in the front passenger seat that works out whether someone is sitting there and how big they are, so the airbag can decide whether and how hard to fire. The recall names '2021 Sienna Hybrid' specifically alongside a long list of other Toyota and Lexus models, and dealers inspect and replace the sensor free (Toyota's codes are 23TB15/23TA15). The reason this dominates one half of the 2021 complaint file is timing: interim letters warning owners of the risk went out in February 2024, some final-remedy letters followed in October 2024, and Toyota said letters would 'continue to be mailed in phases through January 2026'. Owner after owner filed to say the parts were on backorder and that Toyota had exceeded a reasonable time to fix it. Before buying, check this recall against the VIN and find out whether the sensor has actually been replaced or the van is still waiting.

A 2025 recall covering 2021–2025 Sienna Hybrids: 'The bolts for the seatbacks on the third-row seat assemblies may not be tightened properly,' which means a seatback may not hold an occupant properly in a crash. Toyota lists it as failing three federal safety standards — head restraints, seating systems, and child restraint anchorages, the last of which is why this matters more in a minivan than it would elsewhere. Dealers simply tighten the bolts, free, and owner letters were mailed on 1 April 2025 (Toyota code 25TA05). One owner in the file went in for a rattle from the second row, had the recall performed, and was told the remedy addressed the third row only — so if your rattle is further forward, this recall will not fix it.

Not a recall, so it will not appear in a VIN recall search — you have to ask a Toyota dealer for it by name. Toyota's wording: 'Toyota is providing extended coverage under this Customer Support Program for repairs related to excessive corrosion to the wire harness connections at the Rear Motor Generator. Excessive corrosion can cause AM Radio Static during certain drive cycles, or the vehicle may not start.' A Customer Support Program is quiet extended coverage that sits outside the ordinary warranty. On an all-wheel-drive Sienna the rear axle is driven by an electric motor, and this covers the high-voltage floor wiring harness and rear traction motor cable that feed it. Two practical notes. First, the tell is genuinely odd — AM radio static — so if the AM band crackles on a test drive, that is a reason to ask about this program, not a reason to shrug. Second, read the coverage line carefully: Toyota's bulletin states the parts are covered by the New Vehicle Limited Warranty for three years or 36,000 miles, but that is the ordinary factory warranty, not the program. The bulletin summary never states how long the program itself runs. Verify the terms in the bulletin PDF and get a dealer to check your VIN. Toyota's own documents also disagree on scope — one technical instruction says 2021–2022 Sienna Hybrid, a later one says 2021–2024 — which is another reason to check by VIN rather than by year. Salt-belt vans are the exposure.

Another Customer Support Program rather than a recall, and it names 'Certain 2021 Sienna HV' among a long list of Toyota models. Toyota describes the condition as 'a small engine coolant leak that can occur from the flow shut-off valve that can allow coolant to drip on other parts of the vehicle. This can cause "Engine Maintenance Required" to be displayed on the instrument cluster or cause the A/C not to function normally.' That message is the thing to know: on this engine family an 'Engine Maintenance Required' warning is not a reminder to book a service, it can be a coolant fault — Toyota has a separate bulletin tying the same message on 2018–2021 vehicles to a coolant bypass valve fault code. Toyota's bulletin states the valve is covered by the New Vehicle Limited Warranty for 36 months or 36,000 miles; that is the base warranty, not the program, and the program's own window is not stated. Verify the terms in the bulletin PDF. Check the coolant level and ask whether that warning has ever appeared.

A scatter of first-year items shows up in the file rather than any second big cluster. A blind-spot monitor module killed by a corroded internal connector, dealer-diagnosed, quoted at $2,500 to $3,000, with goodwill assistance declined. Rear underbody air-conditioning lines eroded where a rusted steel bracket contacts the aluminium line, leaking refrigerant. Both front struts leaking at 36,000 miles. A rear liftgate strut bolt that failed and trapped a dog inside. Toyota also has bulletins for a 12-volt auxiliary battery that drains at shutdown on 2021 vans because the hybrid control unit does not go to sleep after the van has been towed or jump-started, for engine control unit damage caused by improper jump-starting, and for an abnormal brake feel — a longer-than-usual pedal stroke — when the van has sat for more than five minutes, which Toyota says does not affect braking performance. And one genuine design complaint from three separate owners: on XLE vans with the rear entertainment screen but without the digital rearview mirror, folding the screen down blocks the driver's view through the mirror entirely.

Worth knowing what you are no longer buying. Our mechanic source lists three third-generation problems the 2021 van solves outright. The strut mounts that rotted from water collecting in the cowl now sit under a deflector plate — 'now you're not going to have these constant strut mount failures'. The rear hatch, which used to bend because a single motor lifted it from one side, is now raised by motors built into both gas struts. And brake pad life, which was poor on the old van, is transformed by regenerative braking. The sliding doors are also simpler: the cable is now replaceable separately from the motor and he calls the job easier than on the old van, though he expects the cables to break eventually as they did before. Two things to check that are not faults, just facts: the third-row seat cannot be removed because it contains an airbag, and there is no spare wheel under the van — a spare was a low-cost dealer option, so look in the load area to see whether the van you are buying has one.