My car will not start. No, it is not the battery, starter, or alternator. It appears to be the immobilizer. My general mechanic has spent a lot of time on it, to no avail, but he says the car recognizes the FOB (it also opens and locks the doors still), but most likely the immobilizer is preventing it from starting.
History: I changed my lone FOB’s battery a month ago when it was low and mostly stopped working. It worked fine for a month. Then, my car battery died and it turned out it was very old. My mechanic put in a new battery, and the car would not start. When he opened and closed the FOB, removed/replaced the same FOB battery, it would start again, but only for a day or so, before no longer working. Since this happened after the battery change, he believes the immobilizer deprogrammed. He tried to program a second FOB but it didn’t respond.
The Hyundai dealer near me is AWFUL. They have had this car and my other Hyundai in the shop for months without being able to diagnose/misdiagnosing and charging me for the wrong/unnecessary issues repeatedly. What would you do? Going to them would be my very last resort. I’m afraid this might be a case where I need a software update. Is there any other way to do this or any other service that could help me? Or anything you suggest I try on my own or tell my current mechanic? Many thanks in advance!
This is one of the things that can occur with some vehicles when the battery is disconnected or dies.
It may reset or disable the anti-theft system. The engine may crank but not start because the anti-theft system thinks somebody is trying to steal the vehicle. Again, it may require a special relearn procedure or reprogramming the anti-theft system with a factory scan tool to resolve the problem.
Thank you. So… am I looking for a mechanic with more specialized car-computer skills? A more advanced scanner? I have no car to drive and my general mechanic can’t figure out how to fix it with his scanner, so I’m trying to figure out next steps.
Call an automotive lock smith that deals with key FOB’s, they should be able to flash the ECM or whatever and get it all working again as long as it is the immobilizer keeping it from starting…
How certain are you that this is the problem? 100%? 90%, 50%? B/c if the problem isn’t the immobilizer you may be on a long wild goose chase. If not 100% sure, the first priority is to determine which of the car’s systems is failing, for certain. There are many possible causes for a no-crank. It’s usually possible for a good shop tech to determine which one is causing the problem. The fixing may require specialty skills and equipment.
There are numerous procedures if you Google ‘2017 Hyundai Sonata immobilizer reset’. The procedures in a couple of YouTube videos seem to work. None require any special tools. Have you looked into that?
Thank you. My mechanic’s scanner shows nothing wrong. Alternator, engine, and starter appear fine, and this happened when we replaced the car battery. Doors and dash respond to the FOB, so this is his best guess right now and he suggested a more computer-oriented/FOB mechanic. Local Hyundai dealer has had two different Hyundais of mine for months on end, making incorrect diagnoses, so…
Just to clarify, what is the car doing? Is the engine cranking and not starting or is it not cranking at all?
Are you sure it’s the immobilizer system? You can confirm it by pressing the start button once. The immobilizer system indicator will start to blink if the system doesn’t recognize the key. If the light comes on briefly, then goes out, it’s working properly and it’s not the immobilizer.
I will have to check. That light did come on and I think it stayed on until we opened and shut the fob, then the car worked for 24 hours then stopped again.
If it’s not the engine, alternator, battery, or starter, and the FOB battery is only a month old, what else could it be?
I’m beginning to think there’s no professional mechanic involved. These should be easy things for them to determine. What’s the status of the immobilizer light? Is it flashing? What “it” are you referring to when you say:
My usual mechanic spent many hours on my car and could not get it to start. He is not savvy in computer and FOB related operations. I have had no car for over 2 weeks and the local Hyundai dealer is absolutely horrible. They keep cars for months, overcharge, misdiagnose, and nothing is resolved. I had to take things into my own hands and came here, where I’ve solved problems in the (distant) past, and where my father used to come to diagnose his car issues.
I finally found and have a FOB/programming expert coming tomorrow if I cannot get my car started before then. I would like to try to resolve it ASAP, tonight. I texted my usual mechanic the shared instructions and asked if he could come try that. He said we don’t need a new fuse. I said but those are the instructions for resetting the security system. He said that doesn’t make sense, and I said I was coming here to ask about it.
I’ a diy’er & have no experience w/your vehicle’s configuration. But if I were presented with that problem the first test I’d make is to measure the two voltages at the starter motor during attempted cranking.
Wouldn’t he prefer that you take the vehicle to a repair shop that has the equipment and technician training for that type of repair? He must have better things to do with his time.
If no one can repair a Hyundai, I wouldn’t own one. This is your second or third Hyundai, did you receive it as a gift?
The instructions in post # 6 state to remove the fuse, perform a task, then install the same fuse. Not a new fuse.
He has always been able to fix my cars at my home. He has an advanced scanner that should work, but he has not managed this issue before. It’s driving him crazy. He’d like to solve it. He referred a FOB/programming mechanic who said he is coming to my house tomorrow, but I need the car yesterday.
I have had terrible experiences with shops around here, and he’s been great for years now, so I’m trying hard to solve this before I have to go to someone totally new. One local shop forgot to tighten screws on new parts, twice. Stranded on highway with young kids. Another, one I always trusted, flat out conned me into a “replacement” part that wasn’t, and charged double what they quoted me. It’s hard to find someone good, and when I do I try to make it work.
People make mistakes. Just part of the car repair process. No harm to ask for a partial refund, or a discount applied to future work. I’d expect a shop manager to comply with that request if they agree they were responsible for the error.
I wouldn’t call that a “con” myself. I expect it is pretty common for a shop to replace a part as part of their diagnostic process, just to see the effects. Can sometimes be the most economical way to proceed with a difficult diagnosis. The estimate is just that, not a guaranteed maximum fee. If you need to know the maximum amount you might be charged, suggest to tell the shop manager this before they start. Ask them to phone you for what to do if the price looks like it going beyond that.
