2018 Toyota Sienna Complaints

POWER TRAIN — Filed 06/01/2026

Vehicle: 2018 Toyota Sienna XLE AWD, VIN [XXX], approximately 112,000 miles. Component: Power Train / Automatic Transmission (UA80F 8-speed). The vehicle has developed a pronounced whining noise from the transmission that rises with road speed, accompanied by harsh/rough shifting. A Toyota dealer inspected the vehicle and diagnosed a failing transmission requiring replacement. The symptoms and diagnostic trouble codes match those described in Toyota TSB T-SB-0160-18 ("Transaxle Whine Noise, Harsh Shift, MIL ON, or Reduced Power") for the UA80 8-speed transmission. This is the same failure mode Toyota acknowledged in Customer Support Program ZJC, which attributes the defect to a washer/locking tab that was not sufficiently bent during assembly, allowing an internal nut to loosen and causing progressive internal damage. However, this vehicle's transaxle serial number falls outside the range covered by ZJC, so Toyota has not provided coverage despite the identical defect and symptoms. This represents a safety concern. Based on documented failures of this transmission across the UA80 platform, the condition can progress to loss of power, limp mode, or sudden loss of forward propulsion while driving — including at highway speed and without further warning — creating a risk of a crash or of being stranded in traffic. The vehicle has been maintained through authorized Toyota service. I am requesting that NHTSA investigate whether the UA80/UA80F transmission defect warrants a broader safety defect determination and recall, given the volume of similar complaints across affected model years INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

POWER TRAIN — Filed 06/04/2026

Since owning my 2018 Toyota Sienna, I have experienced hesitation and erratic shifting with my transmission. I have the UA80E transmission which upon research others are experiencing issues with as well. It appears Toyota is not fully acknowledging the problem. The problem is a safety issue as sometimes when you go to quickly accelerate (merging, making a turn while starting from a stop, etc) the transmission hesitates and doesn't engage for a few seconds. This is an ongoing problem with the transmission. Toyota really needs to fix these transmissions!

POWER TRAIN — Filed 02/01/2026

My 2018 Sienna had developed a whining noise when accelerating. After taking it in to the mechanic, they advised the transmission was failing. Estimated price tag of $6500-7000 to repair. The vehicle has less than 140K miles. Looking at different issues with this make/model and year, it seems like its rather common. I bought a Toyota for its reputation of getting at least 200K if not more miles. I called both the dealer and Toyota themselves. Both said too bad, so sad - nothing they could do for me.

POWER TRAIN — Filed 11/01/2025

The contact owns a 2018 Toyota Sienna. The contact stated that while driving 30 MPH and ascending a hill, the vehicle started making an abnormal whining sound and hesitated while accelerating. The vehicle was driven to the dealer to be diagnosed. The vehicle was diagnosed with transmission failure. The manufacturer was notified of the failure. The failure mileage was approximately 126,000.

POWER TRAIN — Filed 01/14/2026

Transmission has been whining. A P27137F Code appeared and the vehicle is only in 2WD mode currently. Concerned to drive vehicle due to further damaging transmission or getting stuck while on the road.

POWER TRAIN — Filed 10/29/2025

My husband and I bought this van brand new 6 years ago. We have taken very good care of it and have had it serviced only at the dealership. We haven’t had any problem with the van outside of regular maintenance. On 10/29/25, I had a van full of children when I felt a slip in my acceleration and a warning light came on that read, “ A malfunction in the electronic control of the engine, throttle, or automatic transmission has been detected. Contact your dealer in order to have your vehicle inspected immediately.” Thankfully, I was able to get it to the parking lot. The van didn’t leave that parking lot until the next morning when we took it directly to the dealership. That is when we were told the solenoid and the transmission had gone out. We had to have the whole thing replaced. The van only had 89,388 miles on it.

POWER TRAIN — Filed 08/04/2025

Transmission Whine and Hesitation. Low gear it will hesitate from stop. Know issue with this transmission. There should be a recall on all ua80 transmissions.

FUEL/PROPULSION SYSTEM — Filed 07/09/2025

Hi, I’d like to report a serious issue with my 2018 Toyota Sienna related to the recent fuel system recall. Since the repair, the vehicle has leaked all of its gasoline not once, but three separate times. One of those times, my family was inside the vehicle, and the smell of gas was overwhelming. The car wouldn’t start, and it was clearly an unsafe situation. Now the dealership is charging me $1,400 to replace the fuel pressure hose and clamp, which, after thorough research and review, appears to be directly related to the process they followed when replacing the recalled fuel pump. I’ve also tried contacting the service manager, but I haven’t received a call back. That’s why I’m now requesting that Toyota open a formal case to investigate this properly. I believe this repair should be covered, and I’m asking for support from Toyota directly.

ELECTRICAL SYSTEM — Filed 06/04/2025

Odometer Fraud. The contact purchased a 2018 Toyota Sienna. The contact stated that while attempting to register the vehicle, it was discovered that there was a mileage discrepancy. The vehicle was a dealer sale. At the time of purchase, the vehicle mileage was 57,000, and at the time of registration, it was discovered that the mileage was 175,152.

POWER TRAIN — Filed 04/24/2025

Whining sound coming from vehicle while in drive and accelerator is depressed. Confirmed by dealership that the transmission is failing and needs replacement.