2021 Hyundai Elantra Hybrid Problems

At around 93k miles my HECU unit apparently malfunctioned at the same time as the left front tire speed indicator. All of my safety features ABS, adaptive cruise control, lane departure, lane keeping etc do not work because of this.

When gas is pressed (even to floor) in drive, vehicle stalls, does not accelerate. Then vehicle jerks into propulsion after revving. Other instances, at deceleration the car will jerk and shake to a stop. I have mentioned the problem at every scheduled maintenance

The contact owns a 2021 Hyundai Elantra Hybrid. The contact stated that while driving 60 MPH during ice and snow, the engine revved, and there was an abnormal sound coming from the Hybrid battery. While turning, the contact stated that the vehicle had unintendedly accelerated. Additionally, the tire pressure warning light was illuminated. The contact believed that the failure was related to the Hybrid battery. The vehicle was driven to the residence, where it remained parked and was not driven since. The manufacturer was notified of the failure. The failure mileage was 44,900.

The headlights and back lights turn off at random times when the headlights are on the automatic setting. This problem happens very frequently at night, putting my family at risk when the lights go off and cannot see what is ahead of us. In addition to a cop pulling me over for not having my lights on and he asked me if I was playing with the lights since they were going on and off and luckily the cop did not give me a ticket when I explained and he saw the problem (he advised me to get on this website and to make a report). I have reported this problem to the Hyundai dealership for the past 3 years and I don’t even think they take the time to investigate. The dealership just keeps telling me that with another update in the software is going to get fixed. But that is not the case. This is a very dangerous problem that is going to get someone killed. Need to be fixed

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.

So the car will come to a dead stop. Then when I give gas, it will not go for 1-2 sec, then all of a sudden it go at high speed by itself. Even when I brake, it will feel like as if I have stepped onto gas. Very dangerous

On a few occasions (3?) the cars’ automatic emergency braking feature activated while driving at both highway and normal speeds. On none of the occasions was there inclement weather or a “slick” condition on the road. The feature would activate, give a visual and audible warning, and then de-activate within a few seconds. When the feature activated, I felt the car jerk a bit to slow down, and sort of swerve in one direction before righting itself. There is a possibility that the feature activated because I had manually enabled the Auto Hold feature as well which I usually do.

When gas is pressed (even to floor) in drive, vehicle stalls, does not accelerate. Then vehicle jerks into propulsion after revving. Other instances, at deceleration the car will jerk and shake to a stop. I have mentioned the problem at every scheduled maintenance

I keep getting intermittent HEV warnings and 12-volt light. The engine then shuts down and I have no power. This has occurred several times while on the highway and this creates a safety hazard. I have been fortunate enough that this happened while I was close to the shoulder, otherwise, it could have been critical. - The failed component(s) are the 12 volt battery and engine shutdown - With the vehicle being without power while on the highway puts other drivers and myself at risk of an accident - I have taken the vehicle to two different Hyundai dealers and they have not resolved the problem - The issue was escalated to the manufacturer Hyundai Motors and they have not resolved this issue. - The 12v battery light and an HEV warning light comes on and then the engine shuts off - This issue has been happening intermittently for the past year and I first notice it on October of 2022

The headlights and back lights turn off at random times when the headlights are on the automatic setting. This problem happens very frequently at night, putting my family at risk when the lights go off and cannot see what is ahead of us. In addition to a cop pulling me over for not having my lights on and he asked me if I was playing with the lights since they were going on and off and luckily the cop did not give me a ticket when I explained and he saw the problem (he advised me to get on this website and to make a report). I have reported this problem to the Hyundai dealership for the past 3 years and I don’t even think they take the time to investigate. The dealership just keeps telling me that with another update in the software is going to get fixed. But that is not the case. This is a very dangerous problem that is going to get someone killed. Need to be fixed

Check Hybrid System alarmed in heavy traffic and derated my car and put me in a very dangerous situation.

At around 93k miles my HECU unit apparently malfunctioned at the same time as the left front tire speed indicator. All of my safety features ABS, adaptive cruise control, lane departure, lane keeping etc do not work because of this.