2021 Toyota Highlander problems

“My 2021 Toyota Highlander XLE began making a high-pitched whining noise when accelerating. When researching this noise, associated with the make, model, and year of my vehicle, it became apparent that the noise is associated with a manufacturer's defect in the [XXX]‑speed transmission (Toyota [XXX]). The cited notification states that the correction for this defect is a transmission replacement that is only covered by the 60,000 mile/5 Year warranty. There are three class-action lawsuits associated with this issue, and I wanted to document my incident in the event that my service appointment with [XXX] Toyota in [XXX], on 11/23/2026 indicates that my transmission is affected by the defect so many have experienced.”

“When traveling at slower speeds and applying the brakes on a slight decline, my 2021 Toyota Highlander HYBRID lurches forward with alarming force. On probably 5 separate occasions, this has nearly resulted in me lurching into traffic running perpendicular to me. I have come within 2-3 feet of lunging into oncoming traffic and I am probably the poster child for defensive driving. I had to push the brake petal forcefully to stop. I have not allowed my daughter to drive my car because of this. I first noticed this maybe 2-3 years ago? That's a guess. Why have i waited? b/c i'm a fool and poor at executive function. I looked it up, and apparently Toyota is aware of this problem (T-SB-0059-23) but apparently has NOT ISSUED A SAFETY RECALL. This is truly shocking to me, considering the recalls i've seen so far with this vehicle have been for things that do not appear as alarming or potentially dangerous as this. According to Toyota, they will only cover this defect up to 36K miles or 36 months (whichever 1st). I called 2 of my local dealerships and neither "service mgr" knew anything about it. Unacceptable. One of them, AFTER they said this, refused to even look up…”

“My 2021 Toyota Highlander is experiencing the exact bumper/under-cover detachment detailed in NHTSA Recall 23V720. In August 2025, an authorized dealer performed the interim 23TA12 clip remedy. That remedy has completely failed. The lower bumper and engine splash shields are unzipping and actively dragging on the ground, creating a severe road hazard. Fred Haas Toyota World on I-45N and Toyota Brand Engagement are both refusing to inspect this failed safety remedy unless I pay an out-of-pocket diagnostic fee. This is a direct violation of the National Traffic and Motor Vehicle Safety Act, which mandates all recall diagnostics and remedies be free.”

“I own a 2021 Toyota Highlander Platinum AWD equipped with the 3\.5L V6 and approximately 77,000 miles\. The vehicle developed a humming/whining, airplane\-like noise from the front drivetrain while accelerating\. The noise increases with vehicle speed and stops when the accelerator is released\. There is no vibration, and the vehicle makes the same noise while traveling straight\. I took the vehicle to an authorized Toyota dealer, Kerry Toyota, and the dealer diagnosed the transmission as the source of the noise and recommended replacement of the transmission\. The quoted replacement cost is approximately $7,600 plus tax\. Toyota previously issued Technical Service Bulletin T\-SB\-0008\-21 concerning a whine or grind from certain 2021 Highlander UA80 transmissions and identifying the front carrier assembly pinion shafts as a potential cause\. My vehicle is approximately 17,000 miles beyond Toyota’s 60,000\-mile powertrain warranty\. I contacted Toyota requesting goodwill assistance with the transmission replacement, and Toyota declined assistance\. I believe there may be many similar cases involving 2021 Toyota Highlanders equipped with the UA80 transmission,…”

“Four days after I took delivery of this used vehicle (April 25, 2026), multiple warning lights appeared at once: BRAKE, ABS, PARK, Check Engine, Blind Spot Monitor Unavailable, and RCTA OFF. An independent Toyota dealership diagnosed the vehicle April 27-28, 2026 (approx. 109,000 miles) and found (1) water leaking into the rear hybrid battery area through a sunroof drain "installed incorrectly," causing a Brake System Control Module low-voltage code, starting issues, a headlight only partially functioning on one side, possible air in the brake system, and a musty HVAC odor; and (2) blind spot monitor fault code C1AC2 (Slave Module Horizontal Axis Misalignment) - the blind spot and rear cross-traffic monitoring systems do not function reliably. At a second visit on May 4, 2026, recalibration was unsuccessful; per Toyota procedure the only remaining option is replacing the right-rear blind spot sensor. The technician wrote the cause is a mystery, "whether it be body damage related or electrical short." Toyota service records show the same C1AC2 code was documented during the selling dealer's own pre-sale inspection, and that in December 2024 another Toyota…”

“On July 25, 2026, while driving my 2021 Toyota Highlander Hybrid at high speeds on the freeway, the vehicle experienced a sudden loss of drive power accompanied by a check engine light and a severe hybrid system error warning. The failure occurred without any prior warning or degradation in performance, forcing an immediate emergency maneuver through traffic to reach the shoulder. The vehicle was towed to Toyota of El Cajon for diagnostic evaluation. The dealership service invoice details the following findings: - Primary Failure: Primary fuel injector failure (direct injection system). - Diagnostic Behavior: The engine experienced severe cylinder misfires under load at freeway speeds when the direct injectors were commanded on. - System Impact: Engine misfires triggered a hard safety shutdown of the hybrid system, immediately cutting motive power to the wheels. - Repair Executed: Replacement of the failed fuel injector assembly Safety Concern: A primary fuel injector failure at highway speeds causes an instantaneous engine misfire under load, which immediately triggers a hard hybrid drive system shutdown. Cutting motive power suddenly in heavy traffic without…”