I need input on this mystery before I go mad.

[Bill]

I would appreciate any input you guys can give me on what the heck was going on with a car I had today. It was an electrical issue and as we all know the symptoms can vary widely. I will try to keep it short but there are a lot of symptoms and details. It was solved by my shop foreman but he can’t explain to me why the thing that fixed it fixed it and it is driving me mad. I know its difficult to figure things out just by reading the info some shmuck posts on a forum 😉 but I guess what I’m really looking for is some ideas, some brainstorming or any bit of info that may get the hamster in my skull running again.

So the patient was a 2012 Sonata 2.0 turbo with about 59k miles, 1,000 more miles of warranty to go, lucky me lol. The keyless entry fobs were not working, the smartkey push button start was not working and the fob had to be inserted into the emergency slot to start the vehicle. Both turn signals were inop, the TPM light in the cluster was blinking and the trunk open light in the cluster was on although the trunk was closed. Also I quickly discovered that the OBD connector did not have power.

First thing I did was attempt to do a full scan. The OBD connector wouldn’t power on the Hyundai VCI scan tool. I ran a power wire straight from the battery to the scan tool and was able to do a full system scan. While it was scanning I used my test light to check all of the fuses in both fuse boxes. All fuses were good. The scan showed 0 active codes and 4 history codes from the smart junction box, B2518,-19,-20,and -21 which is an open circuit code for each of the 4 turn signal lamps. I cleared the 4 codes and immediately every symptom went away and the car seemed perfect. Within a couple minutes it had occurred again with the same symptoms and the same codes set again as history codes. I thought maybe I was dealing with some sort of ground feedback issue but could not find any problems with any ground connections.

At that point I was running short on ideas and ask the foreman his thoughts and he said he’s seen a couple Sonata’s with very similar issues and knows how to fix them. He comes over and takes one of the 15A spare fuses and puts it into an empty fuse slot in the EMS section. I am attaching a diagram of the underhood fuse block and EMS section. For reference he put the fuse into the empty slot between Sensor 1 15A and Ign Coil 20A. Immediately after installing the fuse the problems went away and signals started working. We removed it and the problems came right back, put it back in and the problems went away. What the hell? Why would a fuse need to be installed into a slot that is marked empty? Could it be a misprinted diagram, yeah but the rest of the diagram is 100% accurate. Also lets say a fuse does belong there….where the hell did it go? In theory there should be a blown fuse still installed if a fuse truly does go there. Thoughts anyone?

Attachments:

• Fuseblock.JPG

Topic

[Its me]

That is a puzzle…

The only thing I can think of is that there is an issue with the plastic/metal and putting a fuse in there pushed something back straighter? Squeezed something closer perhaps? like a wallowed out fuse plug that someone stuck an oversized probe into???

Or somehow the added fuse provided a ground? was there any metal in the unused fuse section (probably just one side) that gave it the extra metal needed for a contact (ground I would suspect as well)… Was that metal side on the sensor 1 side?

Sorry, I got more questions than answers too..

Perhaps if you could see the unused plug and which side (if any) there might have been metal on… (I would suspect the sensor 1 side)….

Very weird… Definitely bookmarking this in my Hyundai “good to know” stuff

Edit, Just saw your pic… Would definitely like to take a look at the underside of that fuse panel… wonder if one side or another is getting corrosion/melting and the “new” fuse helps make better contact through an adjoining piece of metal…

Just spitballin right now…

-Karl

[Bill]

Thanks for the reply. I don’t remember the specifics of the metal that was inside the fuse slot although I do remember seeing metal in the slot. Yes there is a lot of “good to know” type of weird stuff and pattern failures for Hyundai. I’m certainly no genius but you guys are always welcome to throw any Hyundai questions at me. You never know it might be something I’ve seen before. I can’t guarantee I’ll help you but I guarantee I’ll try.

[Bill]

I actually did pull the EMS section out of that block to look for damage and it all looked normal. I guess now I’m going to look at the diagram of the back of the EMS block and see if I can figure out which wires go to which fuse and then try to find them on a wiring diagram.

[Bluesnut]

I can’t answer your question without thoroughly going over the fuse block and wiring diagrams associated with it.
However, is it possible the diagram or schematics could just flat be wrong? I’ve run across errors in the past on various models even in factory service manauals.

A few years back I came across an error in a Helm Ford manual provided to Ford dealers) and emailed Helm about it. I got the boilerplate “we believe in the accuracy…” answer.

With a Mitsubishi A/C compressor engagement issue I was extremely frustrated after some hours of digging and then discovered the schematic was in error. Not only was the paper manual wrong but the schematic on ALLDATA was also incorrect. Of course, ALLDATA gave me the same answer as Helm…. 🙁

I understand where you’re coming from as not knowing the cause of a problem grates on me to no end.

[Author]

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