That makes some sense regarding the correlation, however a hardware solution of replacing the entire harness seems extreme. The car had a knock sensor that must have functioned prior to firmware change. I can only make educated guess as to how the code change affected it. Perhaps it needs to be more sensitive to knock input and so they reduced the amount of software filtering. This allows more noise to pass through the software filter and count as knocking. However, this just points to a complete lack of testing and validation of the change. Now, rather than do the testing and fine tune the algorithm, the solution is to shield the wiring? And, rather than implement a hardware filter at the ecm, they replace a complex and expensive harness? I see this kind of knee jerk reaction and less than optimum solution proposed all the time. I hope I’m wrong about the situation but seems likely based on limited information so far. Hope it works in the end but it’s certainly a costly solution for the manufacturer…
To me (software professional) it indeed looks like a lack of testing, but considering that manufacturer now goes through the cycle of getting a number of engines with mechanical issues turning up for warranty, they may be thinking in a way of “hey, this change will not make it WORSE, but COULD give us some costs savings as instead of paying to TOW a customer we will make them to SELF-LIMP-TO-DEALERSHIP” 
Got the car back today, Hyundai tech support has told the dealer they have >100,000 cars Nationwide that they’ve had to warranty after the 953 update. Dealer treated me properly, car is fine, I’m happy.
Seeing they only sold 105,118 of the 2018 Sonatas, they only have just over 5000 to go.
Thanks for updating, and happy they got your car fixed.
The campaign actually covered 13-18 model years. Mine is a 17.
Interesting. I’ve experienced software modifications cause electrical interference problems that later require a hardware solution. Not in cars, but in manufactures developing electronic instrumentation. So such a thing is possible. I’ve never seen that problem require the entire wiring harness be replaced though. It was always replacing a few wires with improved versions and maybe adding some ferrite chokes here and there. But the way cars are wired, in bundles of many wires, possibly hundreds of wires in a bundle, maybe replacing the whole harness is the better solution. The old harness presumably is re-worked back at the factory for later use in another repair. It’s great that Hyundai took care of the OP’s problem with due diligence, and now it is presumably solved. Good on Hyundai for that.
The economics of manufacturing and in this case post-sale warranty fixes is way beyond me, but often it seems like the cost-benefit analysis causes procedures that seem very wasteful of materials because the cost of labor is prohibitive.
That’s very true. Taking that into account, makes even more sense to try and solve it with revised software algorithms if at all possible. Without all the background info, we’re just {insert bodily function here} into the wind…
Same thing happened to me today with my 2018 Sonata with about 6,200 miles on it. I had the firmware update applied about 3 weeks ago and today the car sputtered and flashing engine check light came on and car ran crappy. I limped the car back to the dealership and now they’re telling me I need a new wiring harness which is on back order. At least they gave me a free rental car, but it’s certainly not what I expect from a brand new car with less than 10K miles on it.
I am amazed that Hyundai/Kia still sell brand new cars with this engine without any meaningful plan to fix the issue for good.
Also, don’t know how much research does the regular car buyer do that they still buy this cars (my wife says I am too OCD about cars and most other-normal-people don’t care).
I had this occur on 1/22/19 3 days after the software update. Had it towed in. 3300 miles. They had it 31 days and loaned me a lesser car. It was suggested by the dealer to contact corporate customer support. They have promised a contact in 3-5 business days. Twice. Trying to blow me off. No contact yet.
I tracked why the cable replacement took so long. It had to be newly created, manufactured, exported, imported and delivered. The mfg was somewhere off shore.
As a follow up, I received another email indicating a contact in 3-5 business days. Ha. I found the name and addresses of the head of QC and the VP of consumer affairs. I’ll be drafting a letter to one or both this week.
I have been a customer of Hyundai since 2007 (3 cars) and my daughter since 2001 (4 , 2 leased 2 purchased) so I was generally happy with them until now.
Mine told me they expect that number to to 200,000. It covers Sonatas with the 2.4 engine from 2013-2018 plus a number of Santa Fe’s in they year range.
They’re getting more efficient in handling the issue, and they now know not to bother changing the control harness first, but to go straight to the main harness.
I heard that. Mine was the complete harness change.
I finally talked to consumer affairs yesterday. Their attitude is “ you have your car back and it works. Be happy with that.” He said the fact I received a loaner for the duration was a courtesy, that there is no rule that says they have to supply one. He said they have to pay the car rental place a lot of money. Except the one I had was a dealer registered car, not from a agency.
This problem is going to come back and bite them in the ***.
I don’t agree. The dealer treated me with more care then any dealer I’ve ever dealt with. Hyundai is being somewhat idiotic trying to turn a knock sensor tuned to only detect detonation into one that will also detect a rod bearing knock. Other than this issue, the car’s been flawless for almost 3 years now. I wouldn’t hesitate to get another one.
I have a 2018 Hyundai Sonata. I had the software update done a week ago Friday. The next day I drive 255 miles to St. Augustine,Fl.
No problem until Tuesday when, after golf, the engine malfunction light was flashing. Car was skipping and knocking and couldn’t go over 60 and max RPM OF 1500.
Took it to Hyundai dealer up there where it sits now while I have a loaner which is now back where I live. Told part, wiring harness for knock sensor, is on back order and not known when part will arrive. Have read that this an ongoing problem and have even read, I believe, that it could result in a new engine. Complicated that I need to go north and don’t know if my car will be fixed by then.
I would suggest, if you have a good relationship with the dealer who sold you the car, tell them your issue and ask if they would contact the dealer fixing the car and ask them to make it a priority. Almost acting as your “agent”.
That’s not the problem. The problem is that the part is on back order. The service consultant has, on her own, has had two cases opened with Hyundai customer service.
She is definitely been an advocate for me.
I found out personally even though 'the harness is on backorder, we don’t know when it will be in",20 bucks to the service advisor changed that to “pick it up tomorrow after 3 pm”.