2018 Hyundai Elantra: won't start

Filed Nov 16, 2025 · Electrical, Engine · GA · crash · 1 injury

Initial Fault Code: P0303 Replaced all 4 spark plugs and all 4 ignition coils. The check engine light extinguished momentarily but returned, logging P0303 and a new P0301 Replaced all 4 fuel injectors. CEL extinguished momentarily and then returned, logging P0303. Replaced the entire engine electrical harness. Concurrently, all related electrical components and connectors were meticulously cleaned with professional contact cleaner. CEL extinguished for significantly longer period of time, and then returned, re-logging P0303 and P0301. Thid suggested the ECU was "handshaking" with new components but re-logging the fault upon detecting the persistent core issue. A full compression test was performed. All cylinders reported results within specification. Using a borescope I inspected cylinder walls in piston tops. There was significant carbon residue buildup but nothing out of the ordinary for similar GDI engines. I still performed a PEA GDI specific chemical cleaning. It was a a little smoother afterwards, but the misfire persisted and CEL remained on. I also removed, cleaned, and tested common sensor faults, with no result. Also p0128 code and no start / electrical drain, and engine light started flashing numerous occasions had to stop the vehicle. I tried swapping the coils, but all that proved was that the coil was good, I did a power and ground test, it passed the connector had 12 plus volt power and a perfect resistance to static ground. The signal wire from the coil connector had perfect continuity to the ECU but had OL to chassis ground showing there was no short. A test light was used to see if anything was coming from the signal wire to the ignition coil and that test failed, there was no signal pulse. The diagnostic process has definitively proven a component-level failure inside the engine control unit. See attached file for more detailed information.

Filed Jun 1, 2025 · Engine · NY

Check engine light came on , car was sluggish and stalled on highway , was able to glide over to the side . Would not start . This is the 4th time this happened to this vehicle , in the past I was able to put in neutral and restart . They fixed it 3 times but they are now Hyundai is now saying it needs a new engine.

Filed Mar 7, 2024 · Electrical, Engine · KY

My 2018 hyundai elantra went from 50 MPH to 0 in seconds. I was able to coast to the side of the road. The engine shut off. The engine and oil lights came on . Car didnt turn over after that got it towed to my house and once there checkd the oil and the oil was completely empty. Received my last oil change on 1/31/2024 still had miles left over before getting another oil change. There was no warning or signal notifying of oil low or anything after speaking with service mechaninc they mentioned the engine being shot. There is not even 100,000 miles on this engine and it needs a new one. Contacted dealership they advised no recalls on this model. Hopefully adding another complaint can get the ball rolling so there can be a investigation.

Filed Aug 1, 2023 · Electrical, Engine · CA

UNKNOWN- intermittently - multiple times a day for the last month the car starts making clicking noises like a card in the spokes of a bicycle. Mechanic could not find the cause. UNKNOWN- two times in 2 weeks- while making a turn my car stalled in the middle of an intersection, all the lights on the dash went on, and wouldn't start up again for a couple minutes. Then car starts and runs fine besides the intermittent clicking

Filed May 19, 2022 · Engine, Transmission · AZ

I've had several issues over the years with this vehicle but nothing too major but more so a nuisance. Such as the car hesitating when accelerating, light bulbs constantly burning out on the vehicle within less than a year of being replaced by myself , etc. It is now April 2022 and vehicle problems begin arising, I heard a weird noise coming from the engine (after much personal research learned this is a knocking sound). Which also happens to be the same issue from the prior year models. One day while out running errands the car just completely dies and goes into limp mode while I was turning onto a busy street (very dangerous). I drove it a very short distance back & forth to work a couple of times because thats as far as I felt going safety wise. The engine jerked forward one day but still continued to run. Then one day on my way home from work when I began slowing down to turn into a driveway. The car completely died again. It went into limp mode enough for me to creep and barely park it where I ended up having to get out & push the vehicle. It doesn't turn over or start at all now. The car gave absolutely no warnings no codes for me to turn to regarding what was going on etc. Hyundai says in order for it to be covered under the warranty that I have to provide them with information. Which I have no problem doing. However based on the research that I've done from other Hyundai Elantra owners others have had similar issues. My Car is barely 4 years old & only has about 65,000 miles on it. I went with Hyundai's because I wanted something that would be safe and reliable especially because I had a child coming into the world at any moment. I ended up going with this vehicle which isn't even 5 years old & it has already become a lemon. Hyundai currently has the vehicle as I try to figure out what to do with it. Since I no longer feel safe driving it. There are no warning lamps etc that came on.