Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2020 Subaru Forester owners, lightly cleaned up (personal details are redacted by NHTSA).
While driving the vehicle suddenly stalled and stopped running. The dashboard illuminated with most lights and the check engine message came on the screen. I was thankfully able to get into the shoulder on the road safely without creating an accident or getting injured. The vehicle would not start again and had to be towed to the dealership. I am now out $1800 because I am slightly over my powertrain warranty in mileage on the vehicle. This is a known issue in bulletin: https://static.nhtsa.gov/odi/tsbs/2022/MC-10208664-0001.pdf I am not only disappointed with Subaru of America and NHTSA that this is not already a recall but I am also willing to seek legal action and compensation if this repair is not going to be covered. …
Component/System Defect: Failed Thermo Control Valve (TCV) leading to sudden vehicle power loss / limp mode. Description of Safety Incident: While operating my vehicle at highway speeds late at night, the Thermo Control Valve (TCV) failed catastrophically without warning. The vehicle instantly experienced a massive loss of engine power and entered an aggressive "limp mode," causing a drastic, uncommanded deceleration in active traffic lanes.Due to the sudden reduction in speed and the low-visibility night conditions, a commercial semi-truck traveling directly behind my vehicle was nearly unable to brake in time and narrowly avoided rear-ending us. My family-including an elderly senior and a [redacted] child-was trapped inside the vehicle during this near-miss collision. The vehicle became an immediate hazard on a high-speed highway. …
The thermo control valve malfunctioned causing the check engine light to come on which shut down all the safety features in the vehicle including the front eye sight camera, blind spot warning, the rear automatic braking, lane departure warning, adaptive cruise control, and lane keeping assistance. The check engine computer readout diagnostic trouble code was P26A5 "Engine Coolant Bypass Valve "A" Position Sensor Circuit Range/Performance". The vehicle was taken to a Subaru dealer who found the thermo valve performance was out of spec. The valve was replaced. This vehicle has not been recalled although the manufacturer replaced the part in 2021 vehicles acknowledging the valve was faulty. …
The other day, the check engine light came on & Eyesight was disabled. I take it to the nearest mechanic who tells me that the cooling fans are running too long at idle & this could drain the battery. He also tells me to watch for the engine overheating. The recently checked coolant level had dropped lower than the minimum. I take it to dealer who keeps it for day. Similar to the 2 other complaints, the fault is related to TSB-09-80-21R calling for replacement parts to be installed. Subaru did not do any recall but instead waited for the parts to fail. I have minimal heat & the engine runs cool a lot of the time which affects emissions. My gas mileage is getting worse. The part is on backorder with no estimated time of arrival. I was told to just keep driving it & to let them know if it starts to run rough. …
Our thermo control valve (TCV) assembly failed and caused dangerous loss of speed and control while on the highway. Subaru is fully aware of the defect in their design as they issued a service bulletin to inform their service centers of a new, fixed TCV assembly that is retaining the same part number (a notice only sent to their service centers, NOT to owners). Please see attached. Despite being aware of the defect, Subaru has not voluntarily replaced the defective TCV assemblies or even bothered to notify owners. Instead, they are letting us put our families and other drivers in dangerous situations through sudden loss of control. There are pages and pages of other owners experiencing this dangerous issue and - like me - being surprised to find it's a known issue that Subaru is not proactively fixing (see any of the owner forums like subaruforester.org).
I was driving on a paved two lane rural route and hit a small bump in the road. Immediately, my check engine light came on and all the safety features turned off. Control panel showed multiple safety features off and the Sport mode indicator light blinking. My car only has 17K miles on it and I have had it just over a month. I was able to drive it safely home and when I called the dealership the next morning I was told I could continue to drive it until the service appointment six days later. When I got home, my husband checked it with his CEL reader and got the code for the temperature control valve (an issue known by Subaru). This was confirmed by the dealership and I was told after having driven it for several days that it should not be driven. The repair is being covered under the power train warranty.
At the time,time, car was not fully 2 years old.. its brand new.This is an addition to a post created a week ago. After the dealership offered to detail the interior of the car to solve the sulferic acid feeling I noticed that the flap above the driving wheel started to feel warm. This happened right in the morning in February. I'm not sure if I am feeling an electrical voltage, smelling the exhaust or there's still sulferic acid in the car. Every once in awhile I my hair smells like oil.. Whatever it is it makes your head feel heavy. My toddler feels something because during a drive he will say " hot". This puts our safety at risk if we are smelling the exhaust or feeling voltage while driving in the car. Sometimes it smells like fuel I the trunk of the car or acidic
While driving temperature light, check engine light, all ADAS lights came on as inoperable (cameras, warning, ABS, BSD/RCTA), no heat (including defrost) available to defrost or for cabin. Appointment 3/13 replaced thermo control valve assembly , coolant bypass valve, intake gaskets, fuel line, coolant, total charges $2070. Luckily had extended warranty I bought, that I had to make a claim on. Dangerous to drive (no camera based safety features available, no defrost for the snowy weather, no emergency braking or other collision safety features on, this affected the entire 'eyesight' system). The engine also had no thermo control regulation during this time, affecting not just then, but possible future performance and early aging due to disregulation.
The Thermo Control Valve failed at 33,945 miles. Because of this, the heater, Eye Sight, Cruise Control, Lane Assist, and Collision Brake did not work. The engine was then only running at "Sport" mode. It did not regulate the heat to the oil and could've caused sludge. The problem was confirmed by a Subaru Dealer Service Shop. I only noticed this problem when the blue thermometer light came on the dash board. Usually I wait about 5 min and once the car is warmed up the light goes away. This time the blue thermometer warning light did not turn off and stayed on for the remainder of the trip. When the car was restarted on the same day the engine check light came on. Eye Sight, Lane assist and Collision assist lights were on.
Subaru has a known issue with a Thermo Control Valve in Foresters. Apparently the part is failing all over the place and they redesigned the part and are replacing it. The problem is the part is backordered and the dealerships are telling people it is safe to drive the car. Our car completely shut off at highway speed. I have since learned this is happening to a number of other owners who were also told it was safe to drive it while the part is back ordered. This vehicle has a lot of advanced driver features and some or all of them are shut off when this happens. Very dangerous for them to tell people to keep driving it and the vehicle should be recalled to replace the defective part that is failing.
Transmission complaints in other Forester years
Frequently asked questions
How common are transmission problems on the 2020 Subaru Forester?
NHTSA has 32 complaints about the transmission & drivetrain of the 2020 Subaru Forester, 5% of the model year's 603 complaints.
Is there a recall for 2020 Subaru Forester transmission problems?
No. NHTSA lists no transmission & drivetrain recall for the 2020 Subaru Forester. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2020 Subaru Forester transmission problems start?
Half of the complaints with a recorded mileage happened before about 1,000 miles, and 100% before 25,000 miles.
Is it dangerous?
Owners linked 1 crash, 0 fires and 0 injuries to transmission & drivetrain problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.