2021 HYUNDAI ELANTRA HYBRID Electrical System Problems

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.

Mileage: 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 Hybrid charging system fails once the vehicle is above 75 mph. After about an hour or two, the vehicle will die on the highway. This is a reoccurring issue putting our safety at risk. The dealership cannot find what the problem is. Online forums show similar issues with dealerships unable to solve the problem.

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.

I was driving on the Highway at the posted speed limit when the warning "Check Forward Safety System" came up and remained on my dashboard. The cruise control stopped working also. The light remained on even after stopping and starting the car and has remained on ever since. I have never been in an accident nor has my computer system reported any collision. My Hyundai Blue Link app gives me the following DTC: C162078. It started on [XXX]. My collision detection system does not appear to be working at all and my cruise control no longer works. I'm very concerned about it malfunctioning based on other entries on the nhtsa.gov website. I took the car to Hyundai Service Center and they are trying to convince me this is due to a collision and warranty will not be covering it. They tried to charge me for diagnostic even though I already had the error code on the Hyundai BlueLink App. They confirmed that my computer has zero reports of any collisions. The service tech said, and I'm quoting, "The system is very sensitive and a swift kick could cause it to malfunction." That sounds like a manufacturing defect to me. I have never been in an accident with this car, there is zero visible damage to the front bumper, and my computer has no report of an accident. The dealership urged me to contact insurance. My Major Insurance Company told me this was absurd, would never be approved, and is clearly mechanical. They also mentioned anecdotally that this problem has been coming up a lot for them with modern Hyundai models. Then I called Hyundai Corporate and they have escalated the issue, agree it sounds mechanical, and will be contacting me in 3-5 business days. They apologized profusely so I am still holding out hope for warranty coverage. I believe the dealership is trying to blame me for this mechanical failure to avoid expense on their end. I have had many software-related issues with this car. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

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

My 2021 Hyunadai Elantra HEV Blue 12v battery light comes on and I lose power to the engine and all internal electrical components. It has happened while driving on the highway and it is a safety concern. I have addressed it with the dealership and they stated there were no codes and they canot replicate.

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

I had reported that the horn wouldn't work..especially in cold weather last winter. The horn would work by the time I arrived at dealer. Told nothing they could do as it was working. It has happened 3 times in the last 2 months, finally totally nonfunctional the past 3 days. I called, stopped at dealer to have it checked. The car was returned to me with service person telling me that the horns diaphragm is stuck. When asked if working , he said for "right now." He told me a new horn(s) were ordered. I asked him what he did: he replied, I hit the horn with a rubber hammer until it worked! Well, one mile or so down the road, it didn't work. I checked the internet and there are MULTIPLE instances listed of ongoing issues with the horns on Hyundai vehicles. In the end, I am driving with some hesitance as the horn isn't working. THIS IS NOT ACCEPTABLE IN A CAR 1.5 years in my opinion. Again, after checking on the NHSSA website, NO RECALLS or MENTION of this safety issue! Please escalate this to TOP PRIORITY! If not, anyone's injury or death is worth the wait!

According to the dealership where I bought this car, the ignition coil failed. This has happened two times so far, resulting in two separate trips to the dealership to diagnosis and repair the issue. They were able to reproduce and confirm the problem; however, what caused the coil to go out is unknown. The component has not been inspected by any other sources outside of the Hyundai certified mechanics at the dealership. No warning lights or messages appeared at time of occurrence; however the engine would rev up when switching between hybrid and gas modes causing the car to lunge forward. The car also would lose power and not accelerate placing me in extremely unsafe conditions as this has occurred on the highway both times. The car is currently at the dealership getting another ignition coil installed. The second time these symptoms appeared caused me to lose power while turning into a gas station from the highway almost resulting into a t-bone crash with a semi-truck. I purchased this car end of February 2021.