2021 Hyundai Elantra Hybrid

I am writing to report a serious and ongoing safety issue with my 2021 Hyundai Elantra Hybrid that remains unresolved despite multiple visits to Hyundai service centers and independent repair shops. I’ve also found numerous consumer discussions online describing nearly identical issues with the same model and newer Elantra Hybrid models, suggesting this may be part of a wider systemic defect. The core issue lies within the vehicle’s hybrid system. Shortly after a recent system/software update performed at a Hyundai dealership, a warning message began appearing at random intervals stating: “Check Hybrid System.” This typically first appears after extended driving — often around 3 hours — but once it occurs, the issue worsens if I continue to drive. Each time the warning appears, the vehicle suddenly and drastically decelerates without driver input, becoming dangerously slow and unresponsive, even while traveling at highway speeds. This creates an urgent safety risk, as I have had to maneuver off the road quickly to avoid collisions. After the initial warning, if I attempt to drive the vehicle again without sufficient downtime, the warning reappears much more frequently — sometimes within minutes. The only temporary relief is to stop using the vehicle and allow it to rest for at least six hours, after which the issue may temporarily subside. In every case, I must use the 12V battery reset button to restart the car, which I suspect may be clearing diagnostic codes before they can be properly recorded. Notably, the check engine light disappears after this reset, even if it was previously displayed. Given that the hybrid battery is located beneath the rear passenger seat, I am deeply concerned that if there is an underlying thermal or electrical issue, it could pose a serious or life-threatening risk to passengers. To date, no dealership or technician has been able to duplicate or permanently resolve the problem.

The contact owns a 2021 Hyundai Elantra HEV. The contact stated while driving 65 MPH, the vehicle started to lose motive power with a battery warning light illuminated. The contact stated that on several occasions, the vehicle had to be turned off and restarted for the vehicle to recharge and restart. The vehicle was taken to the dealer, but the vehicle was not diagnosed or repaired. The contact informed the dealer that the failure was intermittent and within an hour the dealer stated had replicated the failure. The manufacturer was notified of the failure. The failure mileage was approximately 52,000.

This is my second time contact and reporting this issue about the vehicle surging unexpectedly and you cannot get it to slow down except by keeping your foot on the brake and pulling off the road. This has happened multiple times since I have had this vehicle. Recently, I had the car in for service and they said they did a recall for the software to stop this condition from happening again. However, 1 month later, it happened and this time it was the worst I have ever experienced as I kept my foot off the accelerator - it surged over 15mph from the speed I was originally at with me doing nothing and it was still gaining. My car was trying to accelerate with my foot on the brake and I had to cross lanes of traffic to get to the side of the road to restart the vehicle. The reason that it was the worst, is that I literally could not begin to control this vehicle. Other times it has happened and I could at least go for a little bit as long as I kept my distance from other cars but this acceleration was beyond out of control. I could have caused an accident or hit somebody. No warnings appeared, no messages or lights.

the h e v warning light comes on when driving. the hybrid battery disconnects from the engine and the car is undriveable. have to pull over, stop the car, turn off the car and then reset the hybrid battery. this has happened twice in last week. thank fully i was able to pull over safely, but this a dangerous situation for me and other cars around me. the car had been taken to the dealership just two weeks ago and they were unable to diagnose the issue

Our problem started a few months ago. At first, we thought it was just a fluke, but this issue has happened too many times to be so. The issues are, the car does not accelerate when we depress the accelerator, we see the tachometer move, but the engine is not actually accelerating. Then at times it will accelerate on it's own, while sitting at a red light, the car tries to move forward despite having our foot on the brake, it acts like we are trying to push the accelerator and the brake at the same time. Even worse, while driving, the car will go into accident-avoidance mode, even though there is nothing in front of us. There are no errors or codes populating on the dash.

On multiple drives the car has "lurched" or accelerated when foot was NOT on the accelerator pedal. These were minor issues, but unnerving when pulling up to park near a structure. Today 3-23-22 I was driving and after about 1 hour of normal operation the car began to accelerate while pressing the brake, and decelerate while pushing the gas. The engine was revving and then slowing down opposite of what would be expected. This is a hybrid vehicle - it felt as if the gas engine was supposed to be spooling up to charge the battery but instead was feeding power to the wheels. there was no engine light illumination from this. I restarted the car and it seemed ok. Honestly, this was scary - trying to move from one lane to the next to an exit to safely exit the morning rush hour freeway. I had to keep my foot HEAVY on the break to make it slow / stop. On two other previous drives the vehicle "lurched" / the car "bucked" once or twice and then the gas engine would not re-engage. the MIL came on, and the car drove on battery power only. I drove off the road, restarted, and the vehicle worked fine. By the time i got the car to the dealer the MIL had cleared and they were unable to pull any codes and deemed the car safe / found no issues.