2024 Toyota Sienna Problems: 6 Known Issues

On the 2021-2025 Toyota Sienna 2.5L A25A-FXS THS II hybrid, on roughly 168,000 fourth-generation Sienna Hybrids built from mid-October 2020 through late January 2025, the bolts that attach the split 60/40 third-row seat backs to the recliner assemblies were not tightened to specification during assembly. With low-torque bolts the seatback may not restrain as designed in a crash, so the vehicles do not comply with FMVSS seating-system requirements and third-row occupants face an elevated injury risk. Because the Sienna is a family and rideshare vehicle that routinely carries children in row three, this is a high-priority open campaign rather than a nuisance item.

On the 2021-2025 Toyota Sienna 2.5L A25A-FXS THS II hybrid, fourth-generation Sienna Hybrids repeatedly go dead at the 12V auxiliary battery, sometimes on nearly new vans. The 12V battery is only replenished by the DC-DC converter while the vehicle is in READY, so anything that keeps drawing after shutdown flattens it over a few days of light use. Documented contributors include the DCM (telematics) module continuing to draw current after shutdown and, on 2022 vans with the hands-free kick sensor for the sliding doors, abnormal kick-sensor operation in cold weather that keeps the system awake. The signature is a van that powers up to IGNITION but never reaches READY, with 'Hybrid system shutting down' and 'Parking brake unavailable' messages and a Christmas tree of unrelated warning lights caused purely by low system voltage.

On the 2021-2025 Toyota Sienna, the 2021+ Sienna is hybrid-only with a 1.9 kWh nickel-metal hydride battery pack. Some early adopters are reporting signs of hybrid battery performance degradation including reduced electric-only driving range, the gasoline engine running more frequently than expected, decreased overall fuel economy compared to when the vehicle was new, and the battery charge gauge not reaching full charge. While Toyota hybrid batteries are generally very reliable, the Sienna hybrid system works the battery harder than the Prius due to the heavier vehicle weight and more frequent engine-off coasting demands.

On the 2021-2024 Toyota Sienna 2.5L A25A-FXS THS II hybrid, fourth-generation Sienna Hybrids blend regenerative braking with friction braking, and the handoff between the two is not transparent. Under gradual deceleration - typically at low speed, on downgrades, or over a bump while braking - the van momentarily lurches forward as though the driver released the pedal and touched the throttle. Owners describe the pedal as 'mush first, then grab.' The behavior appears on vans with only a couple thousand miles, so it is a brake-control software/calibration characteristic rather than worn hardware, and it has generated a substantial cluster of NHTSA service-brake complaints for 2021 and 2022. No Toyota bulletin that specifically addresses the lurch could be confirmed. Toyota's T-SB-0006-21 (February 2021) covers a related abnormal brake feel (a longer pedal stroke) on 2021 Sienna Hybrids.

On the 2004-2025 Toyota Sienna, the lower sliding-door rail and the seam where the rocker panel meets the sill trap salt, grit and water on Siennas run in the salt belt. Rust starts inside the lower door track and in the rocker seam under the sliding doors, then perforates outward and can eat into the structural rocker/frame area. Because the rail is a load-bearing part of the sliding-door mechanism, corrosion here also causes rough or binding door travel and eventually contributes to power-door faults. Owners report the same corrosion-prone rail design persisting into the fourth generation, not only the older vans. Corroded aluminum A/C lines running along the same underbody area are a frequent companion finding, with dealer A/C repair quotes in the $1,700-$2,500 range.

On the 2021-2025 Toyota Sienna, fourth-generation Sienna owners repeatedly report the laminated acoustic windshield cracking from very small impacts, with chips propagating into full-width cracks within minutes - several owners describe a crack starting under the wiper area and running across the glass while driving. Replacement is not a routine glass job: the forward-facing Toyota Safety Sense camera mounted at the top of the windshield must be recalibrated, and dealers commonly insist on OEM glass because aftermarket units can fail camera calibration. That pushes a windshield replacement well past typical minivan pricing and is a recurring unexpected ownership cost on these vans.