2021 Subaru Forester Engine Problems

My 2021 Subaru Forester has a recurring, worsening defect in the Idle Stop/Start (ISS) system that creates a stalling hazard. When ISS shuts the engine off at a stop, the engine intermittently fails to restart when I try to move again. It cranks progressively slower, warning lights illuminate, a continuous alert sounds, and the vehicle cannot proceed until I shift to Park and restart manually. This has left me immobile in live traffic at lights, stop signs, and mid-turn. The system also attempts to shut down in unfavorable moments, such as mid-turn, or as I am already releasing the brake (meaning it was depressed only lightly or briefly); it then tries to restart while still mid-shutdown, producing a pronounced shake. This is not a battery-charge problem. It has occurred even when the battery tested above its rated cold-cranking amps, and after each failure the engine restarts smoothly by manual start, indicating the starter, engine, and fuel systems function normally. I raised this before 2024, but it was not recorded until May 2024. At that visit the dealer performed the TCM reprogramming in Service Bulletin 16-147-24 (Forester, auto start/stop engine speed drop on restart) plus an ECM update. A later visit added another ECM update. A dealer has now identified yet another TCM reprogramming, quoted for a fee. The failure has persisted across all of these updates. Dealer staff acknowledge repeated customer complaints with these exact symptoms and say there is no known effective fix. Because ISS cannot be permanently disabled through any factory control, I must remember to disable it manually every drive to avoid a restart failure in traffic. The vehicle is available for inspection. This is an ongoing, unresolved safety defect that repeated manufacturer software remedies have failed to correct, and it can leave the vehicle disabled in live traffic.

NHTSA ID

11748058

Incident

Jul 1, 2026

While driving this car on April 4, 2026 at around 6PM, I experienced the distinct smell of gasoline. I had driven for about 5 minutes on our way to a local restaurant that is approximately an 8 minute drive from our residence. My wife said that she had just filled the gas tank that afternoon. After arriving at the restaurant, I checked the gas cap to ensure it was tightly sealed. I also checked to ensure no fuel was leaking from the car. After finishing dinner, we I drove the car back to my residence and once again, 5 minutes into the drive, I smelled gasoline. After we arrived home, I check the vehicle exterior for leaks and found no liquids under the car. The following day, April 5, 2026 at approximately 1115 AM, having once again found no liquids or gasoline under my car, I drove the car to my local repair shop; an 8 minute drive. About 5 minutes into the drive, I smelled gasoline again. I parked the car at the repair shop, but while adjusting the parking to fit better between the painted lines, I saw and heard a large puff of smoke from the hood area. I immediately put the car into Park, shut off the engine and ran from the car. After exiting, I saw that the car ignited with visible fire under the engine compartment. I called 911 to request fire department help. No damage to any structures or other cars occurred. Q1 Above: No the car is totaled and unavailable for inspection as far as I know. Q2 Above: I had to run from a burning car. Q3 Above: No. Q4 Above: Yes, the car was inspected by my insurance company, USAA. Q5 Above: No, there were no warning lights or any indictor that there was trouble. I would like to note that the car was brought in to my Subaru dealership service station (Hyman Brothers in Midlothian, VA) for a heater element safety recall several months ago.

NHTSA ID

11731868

Incident

Apr 5, 2026

While driving the car, the engine stops completely. After a few seconds, it can be restarted. It does this several times a week at random intervals. It's very dangerous since it usually happens when we're driving in traffic. The dealer checked it out in July but couldn't find anything wrong. Even though it's a serious safety problem, they said to keep driving it until it does it every time the car is driven or until the car won't run. When this happens, all the dashboard warning lights come on and the word "Eyesight" is displayed with a diagonal line through it. A warning buzzer also sounds. This started last summer with very infrequent occurrences and is now several times a week.

NHTSA ID

11728784

Incident

Mar 25, 2026

Automatic start/stop fails to turn car on - intermittent. Taken it to Subaru detailer miltiple times and paid for services to correct the issue, but the issue persists. Fist time - replaced the battery in July 2025. 2nd time, went on a ride along for 1 hour, issue did not happen, replaced spark plugs, issue persists. 3rd time, updated TCM software, issue still persists. Subaru of America is aware of the issue and have not gotten a resolution either.

NHTSA ID

11728464

Incident

Apr 1, 2026

The contact owned a 2021 Subaru Forester. The contact stated that while driving at approximately 4 MPH and slowing to park, the vehicle accelerated on its own. The contact stated that the vehicle drove out of the parking lot and crashed into a wall. The contact stated that the air bags deployed and that the vehicle had then shifted into reverse (R) and driven out away from the wall and crashed into a parked vehicle and stopped. The contact stated she was unaware of any warning lights. The contact stated that she had 1 passenger in the front seat and 2 passengers in the rear seat. The contact stated that everyone was shaken and achy, but no cuts or other injuries. The contact stated later that the passengers went on their own to seek medical attention. The contact stated that the passenger front bumper, hood, and wheel well were damaged, and the rear bumper on the passenger side had damage from the crash with the parked vehicle. The contact stated that the other vehicle had minor damage to the right rear quarter panel. The police were called and issued a report. The vehicle was towed to a collision repair shop, but had not been repaired. The vehicle had not been diagnosed for the independent acceleration and reverse failures. The contact stated that her insurance provider had not yet declared the vehicle a total loss. The manufacturer was not informed of the failure. The failure mileage was approximately 30,000.

NHTSA ID

11723858

Incident

Mar 4, 2026

Mileage

30,000 mi

Car drains battery. 45,000 miles and has had 3 batteries and have been told it needs another. Dealer says start stop switch, requires a battery of 750 CCA and not the Subaru recommend battery. Car will die in traffic and driver seat adjusts to different positions by itself. Told that these problems will never stop unless I get a higher rated battery than required.

NHTSA ID

11714847

Incident

Jan 6, 2026

On January16,2026 while driving from Houston,TX to Austin TX the vehicle experienced a complete loss of power on Highway 71 W. We were traveling at approximately 70 MPH when the engine completely failed. We were forced to immediately pull over onto a narrow shoulder Our situation at that point was dire: we could not exit the vehicle as other cars were speeding by. Fortunately an emergency vehicle from the Texas Department of Transportation pulled up behind us with his emergency lights flashing. He told us we were in a dangerous situation and, due to our location, he was not able to tow us to safety. Our only option at that point was to allow the emergency vehicle to puss us to a safe location off of the highway. The driver pushed our vehicle approximately 1/2 mile to a motel parking lot. We contacted Austin Subaru, arranged for a tow truck, and proceeded to the dealer. The dealer technician advised us the Thermo Control Valve had failed. We were told this failure was common. The repair was at no charge since Subaru, being aware of the problem, had extended the warranty on this part. The action by Subaru to extend the warranty instead of proactively replacing the part before failure seems blatantly irresponsible

NHTSA ID

11713463

Incident

Jan 16, 2026

The vehicle has experienced four separate engine shutdowns while stopped in traffic. Each time, the engine turned off unexpectedly, requiring a manual restart. One incident occurred near a railroad crossing with my child in the car. The vehicle also lurches forward at low speeds and hesitates when accelerating after being stopped. These issues persist despite service visits. I believe they may relate to Technical Service Bulletins regarding the Auto Start/Stop and battery systems (TSBs #16-147-24, #10232217, #07-218-23R, #10251098). Subaru service staff have acknowledged awareness of these problems. I’m submitting this complaint to ensure the safety risk is documented and investigated.

NHTSA ID

11696842

Incident

Oct 23, 2025

The contact owns a 2021 Subaru Forester. The contact stated that while stopped at a traffic signal, the vehicle stalled. No warning light was illuminated. The contact was able to restart the vehicle. The contact stated that on a separate occasion, while driving over railroad tracks, the vehicle stalled. No warning light was illuminated. The contact was able to restart the vehicle. The contact continued to drive, and two blocks later, the vehicle stalled. No warning light was illuminated. The contact was able to restart the vehicle. The vehicle was taken to the dealer, where it was diagnosed with battery failure. The battery was replaced. The contact picked up the vehicle, and on the drive back to the residence, the vehicle stalled. The contact stated that the vehicle was almost rear-ended by the vehicle behind. The vehicle was towed to the dealer. The dealer replaced the fuel injectors. The contact picked up the vehicle, and the following day, while driving to work, the vehicle jerked abnormally and the vehicle stalled. The vehicle was towed to the dealer; however, no cause for the failure was found. The vehicle was not repaired. The contact stated that the failure persisted. The manufacturer was not notified of the failure. The failure mileage was approximately 32,000.

NHTSA ID

11695458

Incident

May 19, 2025

Mileage

32,000 mi

driving on [XXX] in NJ on [XXX] at approximately [XXX] my car just stopped in traffic and steering locked up and all lights came on dashboard along with a constant beeping sound-I was in the middle of a four lane highway traveling south-I could not get out of my car and feared someone would hit me as I was a "sitting duck" while cars were swerving around me-my only saving grace was that my flashers worked after I turned them on-I called roadside assistance as I was starting to panic and was told they could not help me as I was on a private road-I saw a helicopter overhead and at the same time a police office weaving in and out of traffic behind me to slow and stop the traffic-he then proceeded to push my car off the road with his car to the shoulder and called a tow truck-car was towed to nearest Subaru dealer where they performed a diagnostic test and found NOTHING WRONG WITH MY CAR!! How could that BE?? I was then charged for the test and the tow-have called Subaru customer care several times but they say they cannot help me because the test result showed nothing-Please help me as I no longer have peace of mind driving this vehicle and I am [XXX] who needs to drive long distances several times a month- there were no previous warnings in my car it just stopped INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11684971

Incident

Aug 1, 2025

Vehicle began surging during acceleration. Dealer stated that the Engine Intake Valves had carbon deposits that were causing performance issues including poor fuel economy, increased emissions and running concerns. The valves required a cleaning to correct the issue. This is a 4 year old vehicle with only 38,000 miles, this is unacceptable for issues like this so soon. Estimated cleaning cost is $300 and is mentioned no where in the scheduled maintenance information.

NHTSA ID

11680140

Incident

Aug 12, 2025

At signal/stop sign or in stop and go traffic, Engine shuts down. Car is in park. Engine (or Car) makes beeping noise when this happens. Eyesight disabled shows on the screen (however this has nothing to do with that) There's existing lawsuit for cars until 2020. This problem exists for some 2021 model as well. Similar problem: [XXX] This is a recurring intermittent issue. Can't reproduce consistently INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11677645

Incident

Mar 27, 2025

The Auto-Stop/Start feature frequently fails to properly restart the car, often causing the car to stall during the restarting process, leaving me effectively disabled on a busy road. The battery has already been replaced once.

NHTSA ID

11669728

Incident

Jun 27, 2022

The automatic shutoff that occurs when the vehicle stops to prevent idling, disengaged two separate times in the span of 4 days. Both incidents occurred at very busy intersections and failed to restart both times. When attempting to restart the car, lights came up on the dash, along with beeping, and failed to restart the car after the light had turned green. To restart, the car had to be completely turned off for about 60 seconds and then could be restarted. To avoid having to experience this issue again, or worse - get into an accident - I took it to the shop where they could not recreate the issue.

NHTSA ID

11663231

Incident

Oct 7, 2024

2021 Subaru forester limited- Stop Start when stopping at a red light. Sometimes the engine does not restart when releasing the brake pedal. Message on dash put car in park and press start. Occurred. April 24 2025 and May 5 2025

NHTSA ID

11659683

Incident

Apr 24, 2025

Was stopped at traffic light. Start Stop system was engaged. Engine turned off as normal. When I took my foot off the brake the engine did not engage and the Eyesight warning light came on that the Eyesight system was not functioning. Put the car in park and engaged the ignition button and the engine started. Turned off the Start Stop system and the car functioned normally after that. Have read postings on Subaru forum that this has happened to others.

NHTSA ID

11654189

Incident

Apr 11, 2025

12/14/24-I was stopped at a red light at a VERY busy intersection. The engine was in stop mode by the start/stop feature. When the light turned green, the car failed to start. The entire car shut down, with alarms sounding and dash lights flashing. The entire system had to reboot before I could restart the car. It was a freighting experience. Fortunately, I wasn't killed by traffic zooming by or by some person with road rage. 12/16/24-Issue evaluated by local Subaru dealer. Their evaluation was that when the auto start feature was activated, my car battery was too low to work. There was zero warning about a low battery before this failure in traffic. I had to buy a new battery. The auto start/stop feature is not an enhancement, but a safety hazard. Owners should be able to permanently disable this unnecessary drain on batteries and starters. I did a search, and there are plenty of others that experienced similar issues with their Subarus.

NHTSA ID

11635323

Incident

Dec 14, 2024

At 40936 the valve body needed to be replaced. With such low milage vehicle is having problems.

NHTSA ID

11633969

Incident

Dec 22, 2024

Thermo control valve defective. Not informed one week ago when I purchased car at end of lease. Problem known to Subaru since 2019 or sooner. Would not have purchased if I had been notified about this major problem

NHTSA ID

11594250

Incident

Jun 7, 2024

Vehicle was parked and idling unoccupied for under 5 minutes when an extremely noxious, hot blast of fumes came from underneath the back. Black smoke immediately entered the passenger cabin through the vents and flames were visible in the engine compartment and running onto the ground. Entire vehicle was burned beyond recognition in a matter of minutes. Ten days earlier the TCV, a known problem, had been replaced at a dealership per TSB 09-80-21. The vehicle had been driven under 300 miles since the replacement. Afterwards, a manufacturer rep inspected the vehicle, indicated the fire started in right rear of the engine compartment, could have possibly been a fuel leak, but damage was too extensive to determine the exact cause. The referenced TSB explicitly requires a new fuel line for every TCV replacement.

NHTSA ID

11573729

Incident

Nov 6, 2023

The 2021 Subaru Forester had been functioning normally with no warning lights. About 25 minutes into the drive I had come to a stop light on an upward incline. When the light turned green I moved from the brake to the gas as usual. However the auto-start function on the car failed, causing the engine to stall. A loud clunking sound was heard and the dashboard lit up with multiple lights, although I do no recall which ones were illumined. I attempted to press the gas again and the car did not respond. During this short time my foot was pressing on the gas the car rolled backwards and collided with the vehicle behind me. I continued attempting to press the gas pedal and still no acceleration was made. After parking and restarting the car it has resumed normal function. I have not yet visited the dealership so this issue has not yet been reproduced, nor has the offending system been inspected. I'm summary, the automatic engine start failed at a critical location, putting myself and others in serious danger and ultimately caused a crash.

NHTSA ID

11571429

Incident

Feb 12, 2024

Once or twice a day my vehicle hesitates from a light and I have to almost floor it to get it going again.I have brought it to 2 different Subaru dealers 3 times and they say they can't fix the problem.

NHTSA ID

11569468

Incident

Dec 22, 2023

The contact owns a 2021 Subaru Forester. The contact stated while driving 10 MPH, the vehicle became inoperable. The vehicle stopped independently and failed to respond to the brake or accelerator pedal being depressed. The vehicle was turned off and restarted and returned to normal functionality. The contact stated that the Eyesight detection warning light was illuminated. The vehicle was diagnosed but the cause of the failure was not determined. The vehicle had not been repaired. The manufacturer was made aware of the failure and advised the contact to bring the vehicle in for an extended time. The failure mileage was approximately 34,000.

NHTSA ID

11546597

Incident

Sep 12, 2023

Mileage

34,000 mi

Vehicle auto start stop feature sporadically fails to start vehicle after stop feature stringers. Happened on multiple occasions, at red light, at stop sign, on freeway during traffic jams.

NHTSA ID

11511479

Incident

Dec 20, 2022

My vehicle stalls at stop signs and red lights at Least once or twice a day regularly I’ve taken to the dealer and they said I was the reason it does that but the car is barely 2 years old bought new it has been doing that since last year it needs to be fixed

NHTSA ID

11504591

Incident

Jan 28, 2023