2021 Toyota Sienna Problems

What owners report

Complaints about this model year center on brake feel during low-speed and downhill stops, where owners describe a brief release, slip or surge as the van comes to a halt, and these reports appear across a wide mileage range. A second cluster concerns the third-row seats in the 60/40 stow configuration, which owners say lift or lock into place over bumps because there is no latch holding them folded. A third group of complaints is about the 2021 airbag sensor recall, where owners report long waits for a remedy.

1. 1
   Brakes

   Brakes briefly release or surge while slowing

   • 76 complaints (46%)
   • median 28,800 mi at 3.0 yrs old (3 state mileage, few)
   • 8 mention a crash, fire or injury
   • filed 2021–2025

   Owners describe applying steady pressure to the brake pedal and feeling the braking momentarily let go, often followed by a short lurch or surge forward before braking resumes. Several say they had to lift and re-press the pedal to get braking back, and it happens most often at low speeds, coming to a stop, braking downhill, or parking. Complaints describe repeated dealer visits where technicians either could not duplicate the condition or said it was normal regenerative brake behavior. Reported from low miles up through roughly 30,000-70,000 miles, often in stop-and-go, downhill or parking situations.

   What to check: During a test drive, try slow stops on a downhill grade and light, steady pedal pressure to see whether the pedal feel changes. Ask the seller whether the van has been checked for this symptom and what the dealer said.

   2 excerpts from owner complaints in NHTSA records

   “When braking under a load - such as braking while descending a hill - the vehicle will be slowing as anticipated when the brakes are applied, and then for a split second the vehicle feels like the brakes disengage. The pedal pressure doesn't change. The vehicle may not actually speed up, but it definitely feels like it's no longer decelerating. Then a split second later the brakes kick in again and the car responds as expected. This happens nearly every day I drive the vehicle and has since it was new. I've got 28000 miles on it now. …”

   NHTSA complaint #11483601, filed 2022-09, 28,000 miles

   “Acceleration or surge seemingly while transitioning from regenerative braking to friction braking. Observed numerous instances where at slower speeds, after removing my foot from the accelerator and beginning brake application, a surge or acceleration occurs. In these instances I ensured that my foot was NOT contacting the brake and accelerator simultaneously. There is a distinguishable surge in driveline when this occurs. …”

   NHTSA complaint #11607334, filed 2024-08
2. 2
   Air bags

   Airbag sensor recall remedy not yet available

   • 23 complaints (14%)
   • median 29,400 mi at 3.0 yrs old (4 state mileage, few)
   • 5 mention a crash, fire or injury
   • filed 2021–2026

   Owners who received notice of the occupant classification sensor recall report that the airbag or SRS warning light came on and that no repair part was available at their dealer for an extended period. Some describe the warning lamp appearing along with belt reminders, and several complain about being told to wait for a remedy date that passed. Reported across a range of mileages, from around 30,000 miles up to about 98,000 miles, after the recall notice was mailed.

   What to check: Ask the seller for proof that any open airbag sensor recall has been completed, and check that the SRS warning light goes out after the bulb check at start-up. A dealer can confirm open campaigns by VIN.

   2 excerpts from owner complaints in NHTSA records

   “Recall 23TB15 was issued on Dec. 20, 2023. The remedy was supposed to be out by the 3Q24. I just called dealer service, and there is still not a remedy out. I am driving a car without knowing if the front passenger seat airbag would deploy in an accident. This is unacceptable to go this long with no corrective action plan yet issued. Can you take any action to get the manufacturer to correct this defect?”

   NHTSA complaint #11641188, filed 2025-02

   “Our SRS airbag warning notification went on suddenly for no reason we could ascertain, and we're having to get it repaired outside warranty. The van has around 80,000 miles on it, but is only 3 years old.”

   NHTSA complaint #11631583, filed 2024-12
3. 3
   Seats

   Third-row seats lift or lock up while driving

   • 20 complaints (12%)
   • median 13,000 mi at 1.5 yrs old (3 state mileage, few)
   • 3 mention a crash, fire or injury
   • filed 2021–2026

   Owners of vans with the 60/40 folding third row say there is no latch holding the seats flat in the stowed position, so they bounce over bumps and sometimes pop up and lock into the seated position while driving. Some describe the seat back shifting forward under braking or over speed bumps and striking an occupant. Complaints describe dealers saying they could not duplicate the condition or that it was normal. Reported from very low mileage, some within the first few thousand miles, and at various speeds including city driving over bumps and potholes.

   1 related service bulletin

   What to check: Fold the third row into the floor and check whether it stays down when pushed and rocked; drive over a rough patch with the seats stowed and listen for movement. Also confirm the second-row seats slide and recline as expected.

   2 excerpts from owner complaints in NHTSA records

   “I was in a major traffic accident on 2/14/22. I was rear ended in traffic by a car going high speeds. The headrest on the driver seat popped off and ended up in the second row on the floor. Because the headrest came off during the accident my head and neck were not supported and I am still recovering at this time. Although I'm thankful to have survived this is likely a safety issue. I do have a picture and a police report if needed.”

   NHTSA complaint #11455284, filed 2022-03

   “The third row seats in the new Sienna, like most minivans, fold flat into the floor. However, there is no latch to hold the seats in place when folded. I noticed this immediately after taking delivery of the van in April because when the seats are folded, they bounce a bit over bumps. On web forums for the car, other owners mention this as well. However, twice in the last two weeks while I was driving the car, the seats popped up out of the rear well and latched violently into place. …”

   NHTSA complaint #11423175, filed 2021-07
4. 4
   Seat belts

   Seat belts lock or lose tension

   • 7 complaints (4%)
   • median 13,000 mi at 1.5 yrs old (1 states mileage, few)
   • 1 mention a crash, fire or injury
   • filed 2022–2026

   Owners report seat belts in the second and third rows that lock up and will not release, or that go slack while driving so the belt hangs loose. One complaint describes cutting a belt to free a child, and another says a dealer first denied the problem and later claimed it was fixed but it recurred. Reported mostly in the first roughly 13,000 miles and also at higher mileage in later rows.

   What to check: Pull each second- and third-row belt out fully and let it retract several times, and check that the latch releases cleanly. Ask whether any belt has been replaced or adjusted.

   2 excerpts from owner complaints in NHTSA records

   “This recall has been open for 7 months and a remedy has still not been issued - this doesn’t seem reasonable for a safety concern. I have also several times experienced a failure in the “extra” 8th passenger seat (middle row middle seat) sensor - it alarms that the seat belt isn’t buckled even when that seat is not in use and not even installed at the time.”

   NHTSA complaint #11603010, filed 2024-07

   “The driver-side second-row seatbelt goes slack for no reason while driving. All tension is released, and the loose belt falls forward. This is a serious safety issue for the child riding in that seat with no working seatbelt. This has happened about a dozen times on various days while driving. The dealer first denied there was a problem, then they claimed they fixed it. But it is still happening.”

   NHTSA complaint #11451325, filed 2022-02

Buying note. Take a long test drive that includes slow stops, a downhill grade and rough pavement, since brake feel and third-row seat movement are the two things owners mention most. Also confirm the status of any open airbag sensor campaign by VIN before purchase.

Summary written with AI from a sample of 60 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Where a problem shows a complaint count, every complaint for this model year was matched with fixed keyword rules (written with AI and tested against the sample), and the mileage, age and repair figures are calculated from those complaints; owners' figures are as stated, not verified. Other counts refer to the sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.