The 2021 Sienna marked Toyota's shift to hybrid-only minivans with the 2.5L I4 + electric motors. While generally reliable, the platform has shown some concerning early-life powertrain issues and a few specific hybrid system quirks that deviate from Toyota's typical bulletproof reputation.
Premature Engine Bearing Failure / Piston Ring Issues
Occasional · high severity
Typical onset: 30,000-80,000 mi
Symptoms: Excessive oil consumption (1 qt per 1,000 mi or more), Metallic knocking or ticking from engine bay, Low oil pressure warning, Check engine light with misfire codes, Blue smoke from exhaust on cold start
Fix: This is the big one. Some 2.5L hybrid engines are experiencing premature bearing wear and piston ring carbon buildup, requiring complete engine replacement or short block swap. Not TSB'd yet but documented by multiple dealers. Expect 18-24 hours labor for short block, more for complete rebuild. Toyota has covered some under warranty extension case-by-case, but post-warranty owners are facing massive bills.
Estimated cost: $8,000-14,000
Transmission Oil Cooler Lines Leaking
Common · medium severity
Typical onset: 40,000-70,000 mi
Symptoms: Transmission fluid spots under vehicle, Pink/red fluid visible near radiator area, Transmission temperature warning on dash, Slightly low fluid level on dipstick
Fix: The eCVT transmission oil cooler lines and fittings are prone to developing leaks at connections. Replacement involves removing underbody panels and sometimes radiator support components. 2-3 hours labor, OEM lines are expensive. Catch it early before low fluid damages the transaxle.
Estimated cost: $600-1,200
Hybrid System Inverter Cooling Pump Failure
Occasional · high severity
Typical onset: 50,000-90,000 mi
Symptoms: Hybrid system warning light, Reduced power / limp mode, P0A93 code (inverter cooling system), Overheating warning for hybrid system, Vehicle may not start or run in reduced power mode
Fix: The inverter cooling pump (separate from engine coolant system) can fail, causing the hybrid system to overheat and shut down. Replacement requires draining hybrid coolant, removing battery service plug (safety), and accessing pump under vehicle. 3-4 hours labor. Not covered by hybrid battery warranty on some cases.
Estimated cost: $1,200-2,000
Front Transmission Mount Deterioration
Common · low severity
Typical onset: 60,000-100,000 mi
Symptoms: Clunk or thud when shifting from park to drive, Vibration at idle in drive, Excessive engine movement visible when accelerating, Noise during acceleration or deceleration
Fix: The front transmission mount wears prematurely on these hybrid Siennas, likely due to torque characteristics of electric motor assist. Replacement is straightforward but requires supporting the transaxle. 1.5-2 hours labor. Use OEM mounts — aftermarket doesn't hold up.
Estimated cost: $350-600
12V Auxiliary Battery Premature Failure
Common · medium severity
Symptoms: Vehicle won't start (no ready light), Multiple electrical warnings on dash, Power sliding doors malfunction, Infotainment system resets or glitches, Typically fails between 2-4 years regardless of mileage
Fix: Hybrid 12V batteries tend to fail earlier than conventional vehicles due to constant cycling and powering systems when parked. Located in cargo area under floor panel. 0.5 hours labor. Test battery annually after year 2. Use Toyota True or equivalent AGM battery — standard batteries fail faster.
Estimated cost: $250-400
Fuel Injector Carbon Buildup (Direct Injection)
Occasional · medium severity
Typical onset: 70,000-110,000 mi
Symptoms: Rough idle, Hesitation or stumble on acceleration, Check engine light with fuel trim or misfire codes, Hard starting when engine is warm, Decreased fuel economy
Fix: The 2.5L uses direct injection, and carbon buildup on intake valves and injectors is inevitable without regular maintenance. Walnut blasting intake valves is the proper fix, along with injector cleaning or replacement if bad. 4-6 hours for complete service. Top-tier fuel and occasional Italian tune-up helps but doesn't prevent it.
Estimated cost: $800-1,500
Owner tips
Check oil level every 1,000 miles religiously — early detection of consumption can save the engine
Replace 12V auxiliary battery proactively at 3 years to avoid being stranded
Use Top Tier fuel only and run hard throttle occasionally to minimize carbon buildup
Keep hybrid system service up to date — coolant flushes at 100k are critical for inverter longevity
Great family hauler when it's working, but the engine bearing lottery and hybrid system quirks make me nervous about long-term ownership without extended warranty — buy CPO if possible.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
Fitment notes: Auxiliary 12V battery; hybrid system uses high-voltage traction battery for primary power
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Every control module on the 2021-2026 Toyota Sienna — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
⚠️ Mileage programming required; VIN registration mandatory; digital cluster on higher trims
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Vantage Mobility, LLC (VM) is recalling certain 2021-2026 Honda Odyssey, 2021-2025 Chrysler Pacifica, and Toyota Sienna vehicles equipped with QRT-Deluxe and QRT-Max wheelchair restraints. The retractors may not lock, preventing the wheelchair from being properly secured.
Consequence: An unsecured wheelchair can move during transit, increasing the risk of injury.
Remedy: Dealers will inspect and replace the retractors, free of charge. Owner notification letters was mailed January 27, 2026. Owners may contact Vantage Mobility customer service at 1-800-488-9082.
ELECTRONIC STABILITY CONTROL (ESC):CONTROL MODULE:SOFTWARE · 22V239000
2022-04-13
Toyota Engineering & Manufacturing (Toyota) is recalling certain 2022 Lexus LX 600, Lexus NX 350h, Lexus NX 450h+, Toytoa RAV4 Hybrid, 2021-2022 Lexus LS 500h, Toyota Mirai, RAV4 PRIME, Sienna, Venza, and 2020-2022 Toyota Highlander Hybrid vehicles. The Skid Control ECU software may not turn on the Vehicle Stability Control (VSC) system when the vehicle is restarted after the driver has disabled the VSC system. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 126, "Electronic Stability Control Systems."
Consequence: Driving with a deactivated stability control system increases the risk of a crash.
Remedy: Dealers will update the Skid Control ECU software, free of charge. Owner notification letters were mailed May 27, 2022. Owners may contact Toyota customer service at 1-800-331-4331. Toyota's number for this recall is 22TA03. Lexus' number for this recall is 22LA01.
Performance
Horsepower
245hp
0–60 mph
7.8sec
Quarter mile
16.1sec
Top speed
115mph
Fuel economy (EPA)
City
36mpg
Highway
36mpg
Combined
36mpg
Fuel
Regular Gasoline
Capability & size
Towing capacity
3,500lb
Payload
1,500lb
Curb weight
4,700lb
EPA class
Minivan - 2WD
Wiper blades
Fourth generation (XL40). Complete redesign. All trims use same wiper sizes.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2021 Toyota Sienna 2.5L I4 Hybrid and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.