Hyundai Forums banner

1 - 20 of 20 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 · (Edited)
I have a 2015 Sonata and a few weeks ago, push button ignition stopped working. The dash said "Key not detected" followed by "Press START button with key". It did start when I pushed the Start button with the key. Here are some other tests and observations:

  • I've gotten a few "low fob battery" warnings over the years, and changing the battery always addressed it. This time, I got no such warning.
  • I tried my second fob, which has never been used before and is still in new condition. Same problem.
  • The buttons on both fobs work fine, i.e. they lock/unlock the doors and unlock the trunk
  • The lock/unlock buttons on the front doors don't work anymore. I assume because the car is not detecting the fob.
  • The trunk unlock button on the car works sporadically. I don't know what causes it to sometimes work and sometimes not work.
  • I used to use cheap Ikea batteries, so this time I replaced batteries in both fobs with Energizer Lithium batteries, which were expensive but as far as I know is the best you can buy. Same problem.
  • I've been parking my car in the same driveway for 1.5 years before this issue started.
  • Location of the car has no effect on the issue. My driveway, random parking lot, etc.
  • When the car starts (by pressing fob into the start button) it starts with no hesitation as always. The car battery seems to be good.
  • The dealership did a whole car checkup just a week before this started and noted that my car battery was "good".
  • I tested all the fuses under the steering wheel with a multimeter, and they're all good. The "SMART KEY" fuse reads a negative resistance with the car turned off, which I understand to mean that there was already current flowing in the circuit. That makes sense since the proximity sensor needs a bit of current to function while the car is off. In any case, I swapped out that fuse with another identical fuse and it didn't affect anything. I also pulled the fuse and did a continuity test - the fuse is good.
  • I tried removing the SMART KEY fuse altogether and nothing changed (car still starts by pressing key to Start button).
  • If I open a door while the car is running, it beeps and says "Key not detected". If I hold the fob next to the Start button, the message goes away. There's obviously an extremely short range proximity sensor behind the Start button, and it still works.
  • To my knowledge, every other electrical system in the car works.

Ignoring the chance that both my fobs suddenly failed in the same way at exactly the same time (while still being able to lock/unlock doors), this appears to be a problem with the car itself. I have ruled out:

  • fuse
  • fob battery
  • fob (both are still "programmed" to the car)
  • location of car
  • interference
  • car battery

What is there left to check? Maybe the actual proximity sensor failed? Could the car battery somehow be causing this, even if the dealership said it was good?

Thanks!
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #2 ·
Bump.

I replaced my car battery as a hail mary to fix this issue. It was 6+ years old and would have needed replacement soon anyway.

It didn't work. Key still not detected.

At this point it has to be an issue with the proximity sensor(s) which detect the fob, right?
 

·
Registered
Joined
·
220 Posts
Bump.

I replaced my car battery as a hail mary to fix this issue. It was 6+ years old and would have needed replacement soon anyway.

It didn't work. Key still not detected.

At this point it has to be an issue with the proximity sensor(s) which detect the fob, right?
I read the service manual, apparently both front door handles have a sensor to detect the smart key. So if the both door handles don't work and you cant even start the car inside via push-start, then I don't think its the sensor. Highly unlikely 4 sensors have failed (5 if you include smart trunk). The reason you can start the car by touching the start button is because it is using the transponder inside the FOB (like all non smart key cars have). This is a separate system then smart key. Your car is acting like the smart keys aren't programmed to your vehicle, which would indicate the smart key ECU is messing up or something to do with it. There are ways to troubleshoot this but you need a dealer level scan tool to test all this. One thing I would try is disconnecting the main 12v battery and letting it sit for a few hours. Letting the all the computers power down.
 

·
Registered
Joined
·
314 Posts
I've replaced the smart key antenna in my rear bumper after it failed so I have some experience with this system. There are multiple antennas that detect the smart key fob and the odds of them all failing simultaneously is likely pretty low. It's weird, though, that the antenna in the rear bumper that allows you to open the trunk when the car is locked if the fob is in close proximity to the bumper is working intermittently yet the other antennas aren't working at all. I also don't know for sure which antennas control your ability to unlock the door by pushing the door handle buttons (sensors in the door handles or the smart key antennas inside the car?).

The car has two interior smart key antennas (I think they're both inside the center console), one inside the trunk, and one inside the rear bumper. The one inside the rear bumper is the one that allows you to open the trunk while the car is locked if it detects the fob. From my testing, the sole function of the one inside the trunk appears to be to prevent you from locking your keys in the trunk: if you put your keys in the trunk, close the trunk lid, and then use your other fob to lock the vehicle you can still hit the trunk release button and open the trunk even when the second fob is nowhere near the car and the car will remain locked the entire time. Also, when a fob is inside the trunk it's not close enough to the middle of the vehicle for you to unlock the car doors or start the car so it would seem it's the two interior antennas that relate to opening doors/starting the car. The question now is if both antennas inside the car provide the same function or if one of them is for opening doors/starting the car and the other is to prevent you from locking your keys inside the car, or one of them is for opening doors/preventing locking the keys inside the car and the other is strictly for starting the car, or one is for starting the car, one is for keeping you from locking the keys in the car, and it's the door handle sensors that are for letting you lock/unlock the car with the door handle switch.

Regardless, the fact that neither locking/unlocking the car nor starting the car seem to work would lead me to believe either something has gone wrong with your smart key control module or maybe you've got a loose wiring harness for the various antennas considering the trunk antenna sometimes works. Maybe someone with a service manual can give you explicit directions but I'm pretty sure the control model is behind the glove box to the right of the cabin air filter assembly and requires you to remove both the glove box and the trim panel that's behind it to get at it. If you can get in there you should be able to see if it's the the wiring harness that's come loose.
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #5 · (Edited)
I finally got around to taking my car to the dealership for my remote start issue. They said that the problem is a faulty antenna behind the dashboard, and while the antenna is relatively cheap ($56), replacing it is a very labor intensive job because you have to disassemble the whole dashboard. They said it's a 4+ hour job and will cost $612 (Canadian).

Does this sound reasonable? I don't have the knowledge or facts to say otherwise, so a second opinion would be good.

I'm a bit suspicious because you guys are saying there are multiple antennas in my car, and they all seem to have failed at the same time but the dealership will fix everything by replacing only one of them?
 

·
Registered
Joined
·
1,011 Posts
Does this sound reasonable? I don't have the knowledge or facts to say otherwise, so a second opinion would be good.

I'm a bit suspicious because you guys are saying there are multiple antennas in my car, and they all seem to have failed at the same time but the dealership will fix everything by replacing only one of them?
Try another dealer but don't tell them you've had it diagnosed somewhere else.

The labor to re and re the dash sounds about right. Over the years more fixes require the dash to be removed. I was told by my dealer that four bolts hold the dash in, but that does not include all the other work required for a removable.

Make a written agreement with the dealer that if replacing the antenna does not fix the issue, the work will be NO CHARGE. Don't let them parts chase to diagnose. Also ask for old part back.

Issue may also be a wire or connection issue.
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #7 ·
Try another dealer but don't tell them you've had it diagnosed somewhere else.

The labor to re and re the dash sounds about right. Over the years more fixes require the dash to be removed. I was told by my dealer that four bolts hold the dash in, but that does not include all the other work required for a removable.

Make a written agreement with the dealer that if replacing the antenna does not fix the issue, the work will be NO CHARGE. Don't let them parts chase to diagnose. Also ask for old part back.

Issue may also be a wire or connection issue.
They have a $99 charge for "electrical system diagnostics", so I don't want to pay that too many times. Maybe once more.

I asked the service desk guy how confident they are that the issue is the antenna, and he said 100% sure. But if it takes 4+ hours to reach the antenna and put everything back and they only had the car for 1 hour (which includes a tire swap and brake inspection) then all they could have done is plug in a diagnostic tool into the car's electrical system. Is that tool able to distinguish between a loose wiring harness (as Nougat suggested above) and a defective antenna? Wouldn't the tool detect no signal in either case? I'm not as confident in their diagnosis as they say they are.

Has anyone had any luck with independent auto mechanics who specialize in electrical systems? Is there really anything proprietary about Hyundai's keyless entry system that an experienced mechanic can't figure out? Without a warranty, I feel so vulnerable going to a dealer with a mysterious electrical issue.
 

·
Registered
Joined
·
1,011 Posts
I asked the service desk guy how confident they are that the issue is the antenna, and he said 100% sure.
If he's 100% sure, then get a written agreement for no charge if the issue is not fixed. Also ask if there's a TSB on the issue. If so get a copy to read. Try HERE for TSB.

...then all they could have done is plug in a diagnostic tool into the car's electrical system. Is that tool able to distinguish between a loose wiring harness (as Nougat suggested above) and a defective antenna? Wouldn't the tool detect no signal in either case?
A scan tool will only set a direction, not determine bad connection etc. For me, it's hard to understand a simple antenna is broken, not many moving parts.

Has anyone had any luck with independent auto mechanics who specialize in electrical systems? Is there really anything proprietary about Hyundai's keyless entry system that an experienced mechanic can't figure out? Without a warranty, I feel so vulnerable going to a dealer with a mysterious electrical issue.
As long as an independent has the proper scan tool they should be able to diagnose. But they will charge a diagnostic also. You'd have to ask around and put some trust into them as well.
 

·
Registered
Joined
·
314 Posts
They have a $99 charge for "electrical system diagnostics", so I don't want to pay that too many times. Maybe once more.

I asked the service desk guy how confident they are that the issue is the antenna, and he said 100% sure. But if it takes 4+ hours to reach the antenna and put everything back and they only had the car for 1 hour (which includes a tire swap and brake inspection) then all they could have done is plug in a diagnostic tool into the car's electrical system. Is that tool able to distinguish between a loose wiring harness (as Nougat suggested above) and a defective antenna? Wouldn't the tool detect no signal in either case? I'm not as confident in their diagnosis as they say they are.

Has anyone had any luck with independent auto mechanics who specialize in electrical systems? Is there really anything proprietary about Hyundai's keyless entry system that an experienced mechanic can't figure out? Without a warranty, I feel so vulnerable going to a dealer with a mysterious electrical issue.
The dealership can't charge you for a "fix" that doesn't fix the problem and if they try just refuse to pay since they didn't actually do what you paid them to do. And if you're curious how they diagnosed the problem just ask, someone from the service department should be able to tell you exactly what was done. And if it turns out to be a loose wiring harness at the antenna they're going to have to take your dashboard apart to get at it anyway and that's the bulk of the cost. One thing I would do, though, is if you have them do the work make sure you test EVERYTHING regarding your key fob functionality before you drive away and make them stand there and watch you do it; test the stuff you may not even use like Smart Trunk.
 

·
Registered
Joined
·
1,011 Posts
The dealership can't charge you for a "fix" that doesn't fix the problem and if they try just refuse to pay since they didn't actually do what you paid them to do.
Nothing says "Trust" like a written promise.
 

·
Registered
Joined
·
314 Posts
If he's 100% sure, then get a written agreement for no charge if the issue is not fixed. Also ask if there's a TSB on the issue. If so get a copy to read. Try HERE for TSB.



A scan tool will only set a direction, not determine bad connection etc. For me, it's hard to understand a simple antenna is broken, not many moving parts.



As long as an independent has the proper scan tool they should be able to diagnose. But they will charge a diagnostic also. You'd have to ask around and put some trust into them as well.
OBD readers are cheap these days, maybe check and see if that's something in the error code list that would show up using an ODB reader?
Nothing says "Trust" like a written promise.
Agreed, although trust is a two-way street, i.e. you trusting them to fix it and them trusting you to pay once the work is completed. Whenever I have a lingering, hard-to-diagnose problem I make them wait while I verify that the problem has actually been fixed before I leave which should be very easy in this case. This is also why I pay with a credit card. If the issue appears fixed and it turns out not to be after I leave, I go back to the dealership and inform them they can 1) try fixing it again for free, 2) refund my money, or 3) I call the credit card company and initiate a chargeback. Any decent dealership will warranty their repairs for a period of time, as well, especially on non-wear items.

Any reluctance on the part of a dealership (or any automobile repair business) to provide a detailed explanation on how the problem was diagnosed or to warranty their repair should set off alarm bells in your head.
 

·
Registered
Joined
·
220 Posts
I asked the service desk guy how confident they are that the issue is the antenna, and he said 100% sure. But if it takes 4+ hours to reach the antenna and put everything back and they only had the car for 1 hour (which includes a tire swap and brake inspection) then all they could have done is plug in a diagnostic tool into the car's electrical system. Is that tool able to distinguish between a loose wiring harness (as Nougat suggested above) and a defective antenna? Wouldn't the tool detect no signal in either case? I'm not as confident in their diagnosis as they say they are.
So I looked at the service manual apparently you don't have to take the dash apart. Just have to remove the A/C/Radio control panel. YouTube Link. Go to 7:13 timestamp that white rectangle sticker that has "LPIC" written on it is the smart key antenna. If you look real carefully you can make out part number 95420-C1000 (i think), which is the smart key antenna part number. There are two interior antennas. One in the center console and one behind the A/C control. It looks like clips hold it on, shouldn't take no more than 10 minutes to remove that panel. And another 10 minutes to remove the antenna. Seems like a 20 minute job, with a $40 part. To answer your question a scan tool can absolutely test the smart key antenna. However the bigger concern is how in the world is the dealer telling you its a 4 hour job. If all it takes is removing the A/C it should be very easy and under an hour labor. Honestly I would try removing that panel.
 

·
Registered
Joined
·
220 Posts
Also to add on, unless I keep reading the service manual wrong there is supposed to be an antenna in each door handle. I'm not a technician but I find it so odd that you can't unlock/lock the car door with the smart key. Unless for some reason the interior antenna is linked to the door handles. I can't see that in the manual, the only thing linking the three antennas is the smart key module. The manual also very clearly states that using a scan tool, each individual antenna can be checked. So I would assume they would do that, to diagnose one bad antenna they would have to see on the scan tool that every antenna except that interior one was working. But if that were the case why would nothing else work?

EDIT: OP, what part did they quote you on the estimate?
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #14 · (Edited)
So I looked at the service manual apparently you don't have to take the dash apart. Just have to remove the A/C/Radio control panel. YouTube Link. Go to 7:13 timestamp that white rectangle sticker that has "LPIC" written on it is the smart key antenna. If you look real carefully you can make out part number 95420-C1000 (i think), which is the smart key antenna part number. There are two interior antennas. One in the center console and one behind the A/C control. It looks like clips hold it on, shouldn't take no more than 10 minutes to remove that panel. And another 10 minutes to remove the antenna. Seems like a 20 minute job, with a $40 part. To answer your question a scan tool can absolutely test the smart key antenna. However the bigger concern is how in the world is the dealer telling you its a 4 hour job. If all it takes is removing the A/C it should be very easy and under an hour labor. Honestly I would try removing that panel.
That video is extremely useful, thanks! My driver's seat is on the left side, but I assume all the parts are just reversed compared to the Australian model shown. You're right about the antenna model number: 2015-2019 Hyundai Sonata Antenna 95420-C1000 | Delray Hyundai Parts

When you say there are 2 interior antennas, I assume that one is for the typical 'push to start' ignition and the other is the backup system where you have to push the start button with the fob? Are you sure the LPIC antenna in the video is the main antenna?

Also to add on, unless I keep reading the service manual wrong there is supposed to be an antenna in each door handle. I'm not a technician but I find it so odd that you can't unlock/lock the car door with the smart key. Unless for some reason the interior antenna is linked to the door handles. I can't see that in the manual, the only thing linking the three antennas is the smart key module. The manual also very clearly states that using a scan tool, each individual antenna can be checked. So I would assume they would do that, to diagnose one bad antenna they would have to see on the scan tool that every antenna except that interior one was working. But if that were the case why would nothing else work?
I'm also skeptical about their diagnosis. If the antennas are linked and the smart key module disables other antennas if the interior antenna is defective, then why does the trunk release still work intermittently? Wouldn't it also be disabled? Or if the antennas are not linked, then how would replacing just the interior antenna help with the door antennas? It would make more sense if the smart key module itself had failed.

I know it doesn't help to keep second guessing a "professional" diagnosis, but it's an awfully steep price to fix something that seems pretty simple. It also doesn't help that the guy was being dismissive of all the information I was providing about the issue. If he was paying attention to what I was saying, they might have made a better diagnosis. I guess those guys are trained to follow a script.

EDIT: OP, what part did they quote you on the estimate?
Replacing only the interior antenna, presumably the LPIC from the video.
 

·
Registered
Joined
·
1,011 Posts
So now you know the dealership is either totally incompetent or totally dishonest - or both.

Might want to bring this to the dealership owner, see if he sets the culture there.
 

·
Registered
Joined
·
314 Posts
I'm also skeptical about their diagnosis. If the antennas are linked and the smart key module disables other antennas if the interior antenna is defective, then why does the trunk release still work intermittently? Wouldn't it also be disabled? Or if the antennas are not linked, then how would replacing just the interior antenna help with the door antennas? It would make more sense if the smart key module itself had failed.
The key here is understanding that there are multiple antennas and they do not appear from my testing to all do the same job, so depending on what problems you're encountering it may be an antenna issue, problems with multiple antennas, it might be the smart key control module itself, or it might be a random wiring problem. For purposes of this discussion please refer to the following diagram located HERE.

For example, in the rear of the vehicle there are two key fob antennas: one behind the plastic trim inside the trunk directly above the rear bumper (part #6), and one actually inside the rear bumper underneath the bumper cover (part #7). The one inside the trunk appears to be, from my own testing, to prevent you from locking the keys inside the trunk. The one inside the rear bumper is the antenna that senses the proximity of the key fob and allows you to open the trunk by hand even if the vehicle is locked. The one inside the rear bumper is the one that failed on me that I ended up having to replace. After testing I confirmed that antenna inside the rear bumper has a single purpose and the other antennas do not appear to be tied to its functionality, i.e. if I put the key fob near either of the front door handles I still could not open the trunk by hand if the car was locked, the key fob had to be in proximity to that rear bumper antenna.

There are apparently proximity antennas located in each front door handle and when the key fob is in range of these it allows you to unlock the vehicle by pushing the buttons on the door handles (Component Location (2) in the diagram). These antennas have nothing to do with being able to start/stop the vehicle: if you walk up to the car and place the key fob on the ground below the door it will be close enough to the door handle antenna that you can hit the button on the door handle and unlock the car. But if you leave the key fob on the ground, get in the car, close the door, and then hit the Start/Stop button the car will not start as the antennas to detect that the fob is actually inside the car and allow it to start will not detect the fob either because the door itself is blocking the signal or because they operate based on close proximity. Based on the parts location diagram for the antennas in the service manual it's very likely the antennas near your legs (part #4) and hip (part #5) that detect the fob and allow you to start/stop the car.

There is also an antenna up inside the dash near the nav screen (part #2) and I believe that's the one you've indicated the dealership wants to replace. I don't know what the exact function of that antenna is but keep in mind there's yet another set of functionality you have to account for: the buttons on the key fob that allow you stand, say, 30 feet away from the vehicle and lock/unlock/pop the trunk by pressing those buttons. Since that antenna near the nav screen is so high up, and the schematic drawing makes it look like it's a rather large antenna, it's possible it's the unit responsible for receiving those signals from the key fob when you're standing at a distance since you'd need something with good line of sight for maximum reception. Of course, that antenna may do that as well as being part of the system to detect when the key fob is inside the car, I don't know. And then you've got the smart key control model that's behind the glove compartment (part #3) that you can see by just removing the glove compartment door.

I'm not a Hyundai service tech nor am I a licensed mechanic, but based on what you described in your original post I'd be really surprised if replacing that antenna represented by part #2 in the diagram is going to fix the problems you described unless all the affected antennas are wired in series and there's a fault in there somewhere. Based on my own experience with the antenna in my rear bumper going bad I can tell you that absolutely no other key fob functionality stopped working when that antenna broke; I was still able to start/stop the car, unlock the doors by standing next to them with the fob in my pocket, use the buttons on the remote from a distance, etc... I'd suggest you talk to the service manager and ask them why that antenna up in the dash has anything to do with being able to intermittently open the trunk by hand if the vehicle is locked and you're standing at the rear with the key fob in your pocket. As well, when it comes to the buttons on your door handles not working anymore I decided to do a little test: I just now went out to my car, held my key fob in the middle of the windshield with my left hand while hitting the door handle button with my right hand and the doors would not unlock. This tells me that antenna up in the dash has nothing to do with locking/unlocking the doors and the proximity antennas in the door handles are what is dedicated to that functionality.

So here's a question...when they told you they needed to replace an "antenna" in the dash is it possible they were simply misspeaking and actually meant they have to tear your dashboard apart to get at the smart key control module in behind the glove compartment?
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #17 ·
Thanks for the detailed post!

So here's a question...when they told you they needed to replace an "antenna" in the dash is it possible they were simply misspeaking and actually meant they have to tear your dashboard apart to get at the smart key control module in behind the glove compartment?
I don't think he misspoke, because this is what he wrote on the invoice/quote:

REMOTE START DOES NOT WORK- BATTERY REPLACED
100 INSPECTED AND SCANNED FOUND VEHICLE NEED IN CAR ANTENNA KEY


The service desk guy was dismissive of me when I was describing the issues, so it sounds like he also ignored me telling him that the door handle buttons also didn't work. He didn't mention door handle buttons in his diagnosis in person, and the writeup above doesn't mention it either. I think he left it off the technician's work order, so it wasn't even considered in any investigation that was done on their side. He never once said smart key module or anything like that - he only talked about an antenna. I also assume the smart key module is more than $56 he said it would cost for parts. Overall very disappointing experience, and I won't be going back there.
 

·
Registered
Joined
·
314 Posts
Thanks for the detailed post!



I don't think he misspoke, because this is what he wrote on the invoice/quote:

REMOTE START DOES NOT WORK- BATTERY REPLACED
100 INSPECTED AND SCANNED FOUND VEHICLE NEED IN CAR ANTENNA KEY


The service desk guy was dismissive of me when I was describing the issues, so it sounds like he also ignored me telling him that the door handle buttons also didn't work. He didn't mention door handle buttons in his diagnosis in person, and the writeup above doesn't mention it either. I think he left it off the technician's work order, so it wasn't even considered in any investigation that was done on their side. He never once said smart key module or anything like that - he only talked about an antenna. I also assume the smart key module is more than $56 he said it would cost for parts. Overall very disappointing experience, and I won't be going back there.
No problem on the detailed post, I've been down this road and it can get a bit hairy so hopefully what I laid out is useful. As for the dealership, yeah I'd go somewhere else. The dealership I go to actually documents in writing all issues that I report and tailors the fixes accordingly. If yours didn't even document the non-functioning door buttons that's definitely concerning as they very likely had no plans to fix them and you would have gotten your car back with stuff still non-functional.
 

·
Registered
Joined
·
1,011 Posts
Thanks for the detailed post!

I don't think he misspoke, because this is what he wrote on the invoice/quote:

REMOTE START DOES NOT WORK- BATTERY REPLACED
100 INSPECTED AND SCANNED FOUND VEHICLE NEED IN CAR ANTENNA KEY


The service desk guy was dismissive of me......
The problem is believing the "service desk guy". They are salespeople, not technical people. Their job is to sell more service.
 

·
Registered
Joined
·
1,011 Posts
Some general info on key FOB start problems. Go down about half way to get to the, "When Things Go Wrong" section.


After reading I would guess that our system is on a CANBUS network. I think a factory scan tool is probably needed.
 
1 - 20 of 20 Posts
Top