Although I advised against the purchase of this vehicle after the test drive didn't feel right to me, my son loved the car so I helped him get a loan in Dec 2018. In June, I asked my son to take my car for an oil change so i drove this car for the day and the first words out of my mouth when I arrived home were "that car is dangerous....it's an accident waiting to happen" I proceeded to tell him how it kept shifting hard or late and sometimes I'd have to floor it to get it to move and other times I'd barely touch the gas and it'd leap forward....he said "Mom, thats just how this car drives...I said, I drive a Hybrid too...it doesn't drive anything like that!" I was literally scared driving his car, and I insisted he take it to the dealer.

A couple weeks later (July) he finally did and they found absolutely nothing wrong with it. Clean bill of health. I'm no mechanic but major mechanical failures do not happen overnight....right? If this cars behavior scared me shouldn't they have seen some kind of evidence that there was a problem brewing?? 5 weeks later he's driving to work when his car starts shifting erratically, an alarm starts to sound and a warning message appears "hybrid system warning, safely stop and do not drive" He pulls over and calls me in a panic. The vehicle is towed to the dealership who later tells us that some sensors needed to be replaced along with a harness of some kind and I want to say a 3rd thing but after 7 weeks of BS dealing with this car I can't remember exactly but regardless they said fixing these things would fix the problem; they quoted me $1000.

I proceeded to take the car to my trusted repair facility and based on the info from the dealer and without knowledge of what the parts would cost exactly they quoted me $750-800. Sold. A couple days later they call me confused about the dealer quote because one of the parts alone cost $800....how could they quote me $1k? This made them wonder if the dealership even looked at the car or if they simply went off the Technical Service Bulletin.

My mechanic called the dealership who couldn't or wouldn't confirm or deny if the car was physically examined or even driven. Seeing as the sensors in question could cause erratic shifting they replaced them; the harness was more like a this will have to be replaced eventually kind of thing so they skipped it until they new more. No change. The new sensors kept registering zero which he explained to me as basically the communication between the sensor and whatever isn't going thru so again he called the Hyundai service dept and asked their opinion and they could offer no insight. Here we have a list of things that Hyundai says causes the problem that this car is experiencing and replacing all of them wouldn't have fixed this sensor issue.

Not a single Hyundai technician, Hyundai TSB, Manual, NOTHING pointed my mechanic in any direction that could answer why this is happening or where to look next. Hyundai's ONLY advice was "Replace the transmission". Thats it. REPLACE an entire component of an engine because we have no idea how this piece of machinery works....thats what I heard. My guy....being such a thorough and meticulous mechanic couldn't just accept their answer to the problem; to him the symptoms didn't add up to a failed transmission. He spent more hours than he should have to no avail. At this point it's been a month or so and we've paid $1000 so far that when all is said in done was a waste of money. We eventually came to the conclusion that replacing the transmission was the best option to put this problem to bed. Another $3000 later my son now has a used transmission with a 90 day warranty and the countdown begins.....

After the job was done my mechanic and another mechanic examined every inch of the trans they pulled out and couldn't find anything wrong with it; mind you they didn't take it apart and look at every little component so the problem must lie deep within but how is there zero documentation of the inner workings of these transmissions? We took out a $9k loan for this car 10 months ago and a $4000 pill is very hard to swallow when you see dozens of stories across numerous forums of people having to replace this transmission long before any trans should have to be replaced. How many transmissions have to fail before Hyundai takes responsibility?

Less than two weeks after picking up car for a complete transmission replacement, I experienced another catastrophic failure on a 70 mph highway. Going uphill at a slight grade the car started to rev but would not accelerate very well. I thought to myself "I'd better bring this in for a transmission check". Maybe the Hyundai dealership did not adjust the transmission properly. Suddenly, I heard a loud bang. It sounded like a metal part broke apart. The the dashboard displayed -> "Hybrid System Warning: Safely Stop and Do Not Drive" and there a loud alarm sound and I had to quickly pull over into the shoulder. The battery charged to FULL - This had never happened before. The battery is always at 1/2 or a little less but the bar went to FULL. The alarm and message remained for an hour and the gas engine was running. The battery went to just under FULL. When the two truck came I shut off the car. Then the tow truck driver restarted the car and the lights were all off and he drove it onto the truck. It's still at the dealer. They don't see anything wrong and just detected a code "06" which detects a differential between the wheel speed and the engine. Further testing by the auto mechanics is required. I suspect that "new" "rebuilt" transmission is bad. Yet another catastrophic failure on the road and near accident situation. Not good. This is a dangerous car. Hyundai should recall them all until they put in good diagnostics and preventative maintenance. It's a miracle no one has been hurt or worse with these cars. This is not an acceptable situation. I will stay away from Hyundai because of this from now on and this car is my fourth Hyundai. I feel their quality has gone way downhill over the past 10 years.

Update from Mar 24, 2017: Resolution: It turned out to be the transmission again. In fact, they had to replace the transmission two times before they could give me the car back. There must be a real problem with the 2012 Sonatas. Hyundai should give us all new cars. Maybe this should be a class action lawsuit.