2021 Toyota Highlander engine problems

Filed Sep 30, 2026 · Engine · KY

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, including vehicles experiencing comparable whining or grinding noises and premature transmission\-related failures\. I am reporting this because an internal transmission problem that develops shortly beyond the powertrain warranty may worsen and could potentially result in loss of vehicle propulsion\. I believe the federal safety agency should review this issue along with similar complaints involving 2021 Toyota Highlanders equipped with the UA80 transmission\.

Filed Sep 24, 2026 · Engine, Steering · TX

I bought a vehicle in cash three weeks ago at Universal Toyota located at [XXX] . Two days later, I called the sellers [XXX] and [XXX] to have a noise fix /checked. It turns out the transmission is bad/damaged and of course it's not safe to drive. Universal Toyota don’t want to fix it (expensive) INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 17, 2026 · Brakes, Electrical · 123,000 miles · CA

The contact owns a 2021 Toyota Highlander. While driving 20 MPH uphill, the messages "Engine Failure," "Brake Failure," and "Pull Over to A Safe Place, See Owner's Manual" were displayed, and several unknown warning lights illuminated. The contact turned off and restarted the vehicle, but the failure persisted. After a second restart, the message "See Dealer" was displayed with the check engine warning light illuminated. After a third restart, the vehicle was driving rough while the accelerator pedal was depressed. The vehicle was taken to the dealer. The manufacturer was notified of the failure by phone. The failure mileage was approximately 123,000.

Filed Jun 22, 2026 · Engine, Transmission · MS

I own a 2021 Toyota Highlander with approximately 127k miles. The vehicle has developed a noticeable whining/whirring noise during acceleration. The noise appears to originate from the drivetrain/transmission area and has become increasingly noticeable over time. The condition occurs every-time during acceleration and is present under normal driving conditions. I am concerned that this may indicate a transmission or drivetrain-related issue that could affect vehicle reliability and safety. I have found reports from other 2021 Toyota Highlander owners describing similar symptoms involving whining noises during acceleration. The vehicle has been inspected by a Toyota dealership. And is certified through Toyota. The vehicles was bought new from the Toyota dealership and has had all service done through Toyota. I am submitting this complaint so the federal safety agency can evaluate whether this condition is part of a broader pattern affecting similar vehicles as a defect in the original transmission built in the SUV.

Filed Jun 4, 2026 · Engine · TX

Transmission leak requiring torque converter replacement

Filed Apr 30, 2026 · Engine · CA · fire

My vehicle was parked for about an hr 30 min , and it started smoking from dashboard area and immediately went into flames .

Filed Apr 27, 2026 · Engine, Transmission · PA

Car makes a high pitched whining noise at low speeds of approx. 10-30 mph

Filed Apr 15, 2026 · Engine, Transmission · TN

Transmission has failed as have many others of the same year make and model without acknowledgement of a manufacturer defect

Filed Apr 10, 2026 · Electrical, Engine · GA

The vehicle experienced a transmission failure at approximately 62,000 miles, which required a transmission replacement. Toyota replaced the transmission with a rebuilt transmission. Immediately after the repair, the vehicle began experiencing multiple issues that were not present prior to the repair. The vehicle initially would not reverse, and the battery was drained shortly after the repair was completed. Following the repair, the vehicle has continued to experience ongoing electrical malfunctions, including dashboard warning lights, system alerts, and dash lights flashing during remote start. The vehicle has also developed a rattling noise underneath the vehicle. The exact failed component has not been clearly identified. The dealership has provided changing diagnoses and has not provided written diagnostic documentation despite requests. The vehicle has been inspected by the dealership multiple times; however, the issues have not been resolved. During a recent diagnostic, the dealership stated that the catalytic converter is now the issue, but this does not address the ongoing electrical problems. These issues raise safety concerns due to unpredictable vehicle behavior and potential failure of critical systems while driving. Warning lights and system errors began appearing after the transmission repair and have continued since that time. The vehicle is available for inspection upon request.

Filed Apr 8, 2026 · Engine · MI

When accelerating at all, the engine emits a whining noise. The only time the whine stops is when the foot is removed from the pedal. It does not whine at idle. I believe it is the transmission going bad. The problem has been confirmed by a local service center. No warning lamps or messages have appeared.