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Will report in 10 days, thanks again for all the help guys :)
Well on my car, sandpaper wasn't enough. I had to resort to using an old used screwdriver (that I don't use as a screwdriver anymore) and a small hammer. I used that pair to chip the rust away. The rust scale is quite hard and the impact force helped to shatter the scale on the surface.

Here's a before pic from my car. You can see the built-up rust scale towards the top of the sensor mounting surface:
Wood Automotive tire Motor vehicle Gas Automotive wheel system


And here's another shot with a flashlight angled in such a way to try to accentuate the existence of the rust layer:
Automotive tire Rim Gas Automotive wheel system Nut


And here's a pic of the mounting surface all cleaned up:
Automotive tire Rim Motor vehicle Automotive wheel system Gas


So I don't know if that is what's going on with your car, but certainly worth a look. If that's not it, we'll keep working on it. :)
 

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Discussion Starter · #22 ·
@ chase206

Definitely a possibility for particles to interfere I know that. I did my best to spray clean the area after I sanded the knuckle etc. but still....

@ Tiberius

Your case is a lot worse than mine to be honest. Mine is sub 50k car and this is how it looked like BEFORE sanding (just some surface rust):

Tire Automotive tire Wood Motor vehicle Rim


Then I sanded it and got to "rather" clean surface before mounting the new sensor....that fixed nothing :D

After the vacation, I'm cleaning the whole thing again and putting the sucker on the oscilloscope...

Thank you all crew once again, really appreciated :)
 

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Based on your picture, I would also clean the OD of the tone ring.
 
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Mladen, Yeah, your mounting surface doesn't look nearly as rusty as what I was dealing with. Looks pretty clean.

So put the scope on it when you get the chance and we'll go from there. Just be careful about polarity and connections, etc. I don't know how the Tib sensors are connected to the module, but usually scope ground sides are connected together at the scope chassis. The point is, if you probe both fronts sensors at the same time, you can may connect some of the wires sensor together through the scope. And if the sensor wires are not already referenced to each other at the module, your system may not like that.

In my case, the sensors were already ground referenced at the module, so as long as I paid attention to polarity, I was OK.
 

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Discussion Starter · #25 ·
Hi to all,

I'm back with bunch of measurements and a bad news.

TLDR:
It's NOT a mechanical problem (tone wheel, wheel bearing, signal strength, interference etc.).
Everything is pointing towards HECU :(

Does anyone know if I can replace HECU computer while ABS pump is still in place?
(Meaning, without messing up with the hydraulic system.)

I know there are 4 Allen screws but access is kinda hard for lower left one due to the ABS pump holding bracket.

---------------------------------Long version-----------------------

1. Done multiple oscilloscope measurements - all checks out fine
  • peak to peak over 130 mV when crawling up to 3 Volts when speeding up
  • waveform is a nice sine
  • also measured direct voltage on the FL sensor and it is showing the same voltages this confirming OSC validity

2. Super cleaned the tone wheel - no change

3. Switched wires FR to FL sensor harness and vice versa (trough cabin with 4 wire cable with exact connectors)
  • cleared errors with Cascade
  • Result: - C1200 - FL sensor Open/Short (and I'm feeding FR signal to that)

4. Fed a signal once again to E37 pins 1 & 2 from the signal generator
  • found that when signal has abrupt change in frequency, the computer cuts it off
  • when signal is constant (e.g. 120 Hz) it does not cut out even during driving over bumps etc.

--------------------------------------------------------------------------

Thanks to all for reading, will report back
 

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Well none of that sounds like good news.

When you said you switched the wires for the sensors left and right:

"Switched wires FR to FL sensor harness and vice versa (trough cabin with 4 wire cable with exact connectors)"

Can you provide some more detail about that? I'm not sure I understand what you did.

Also, I've got a 2006 here... Do you know if the 2006 system is the same as the 2003? I could maybe do a little poking around here.
 

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Discussion Starter · #27 ·
Hi Tiberius, sure I can.

So I made a 4 wire cable with connectors similar to this:
Product Gesture Rectangle Font Electronic component


Then I removed both wheel splash guards and connected FL sensor trough that newly made cable to a ABS sensor harness in the RIGHT wheel well and vice versa.
Thus I'm effectively feeding FR sensor input to where HECU expects FL ("faulty") signal to arrive and FL signal to where it expects FR signal.

This is the image of the FL wheel well connections (the same is in the FR well):
Hood Automotive exterior Cable Electrical wiring Bumper


So basically the front sensors are wired in "X" to counter-feed the signal.
Since absolutely nothing changed, the problem is definitely not of the mechanical nature (knuckle, bearing, tone wheel etc.).

Only things left are wiring and ABS HECU, and since I checked the wiring multiple times it's looking bad for the HECU.

Hope it clears it up and thanks again for all of your help :)
 

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OK, I think I understand what you did with the sensor wiring. Let me describe it back to you just to be sure - "You made a four wire cable about three meters long, and used that cable to cross connect the two front sensors by connecting the FL sensor into where the FR sensor normally connects, and vice versa." And after doing that, the detected fault stayed with the FL corner of the car. If that's the case, then I would agree that you have eliminated mechanical issues and are looking for some sort of electrical issue.

So also if I understood your cross cable correctly, then you were still using all of the original wiring between the HECU and the corners of the car, Is that correct?

The reason I ask is if that is correct, then there is still a possibility that your fault is in the wiring between the HECU and the connector in the FL wheel well. And considering how difficult it would be to replace or try to repair the HECU, I would want to exhaust all other possibilities before digging into the HECU itself.

I have not looked at the connector style used on the HECU, but I would consider de-pinning the FL and FR wires from the connector and swapping them. Then check to see if the problem stayed on the FL side, or moved to the FR side.

I know it can be risky to de-pin connectors without damaging contacts, but I would look into that before I pulled the HECU apart. You could do it by cutting into the harness also to swap the wires, but it wouldn't be as elegant or reversible.

I'm guessing by your location that it's not as simple as going to a junkyard and picking up a connector off a donor junk vehicle? If you could do that, it would help to use a junker part to learn how to take the contacts out of the shell before you did your real one?
 

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Here's a pic showing what I was suggesting about taking the sensor pins out of the connector and swapping them around. Take the connector shell apart and remove the contacts from pins 1 and 2 and swap them with the pins from 19 and 20:

Musical instrument accessory Rectangle Automotive lighting Gas Gadget


It's always a little risky to take contacts out of a connector shell. Some are easier than others, but I've never messed with any of the Hyundai connectors so I don't know how hard it is to get the contacts out without damaging them.
 

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Discussion Starter · #30 ·
Hi Tiberius, thank you once again for having patience with this issue, your help is highly appreciated!

"So also if I understood your cross cable correctly, then you were still using all of the original wiring between the HECU and the corners of the car, Is that correct? "

100% correct, meaning that I still have the same wire from the car wheel well up to ABS E37 connector!

"And considering how difficult it would be to replace or try to repair the HECU, I would want to exhaust all other possibilities before digging into the HECU itself.
I have not looked at the connector style used on the HECU, but I would consider de-pinning the FL and FR wires from the connector and swapping them. Then check to see if the problem stayed on the FL side, or moved to the FR side."


Agreed and completely plan to do just that. The only problem is that I'm having trouble depinning the harness.
I tried multiple times and it has some sort of locking mechanism that I just can't understand.

I was able to pull/push the white part up/out towards the main groove, and that white part seems to be the "lock". However, that is about as far as I managed to get unfortunately....

Rectangle Musical instrument accessory Electrical wiring Gas Audio equipment



I don't have the possibility to pull the part from the junkyard as you noted. Tibs are not that common here in central EU.

What I plan to do is connect the sensor directly with the wire to pins 1 & 2 from the back side trough waterproof rubber on E37 backside.
I'll use ultrathin contact probes to try to preserve the proofing.

Thanks a lot for all the ideas, I'll keep reporting!
 

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What I plan to do is connect the sensor directly with the wire to pins 1 & 2 from the back side trough waterproof rubber on E37 backside.
I'll use ultrathin contact probes to try to preserve the proofing.
Yeah, if you can't get the contacts out of the E37 shell, then back probing into E37 is the next best thing. You won't be testing the interface between the contact inside E37 to the pin on the HECU, but you should be testing everything else at least. Certainly worth trying.

Only other thing to keep in mind is that the error code says "open or shorted", and if the wires are shorting, that could still happen even if you stick new wires into the back of E37. In other words, if the wires going to 1 and 2 are shorting inside the harness somewhere, the error may still occur even if you run parallel new wires. You will be able to rule out "open" but you will not be able to rule out "short".

So I'm no Hyundai expert, but looking around a little, it appears the same (or very similar) HECU was used on other Hyundai vehicles of the same vintage. Point being... Maybe Tibs are not easy to find where you are, but Sonatas or Elantras might be more prevalent?
 

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Discussion Starter · #32 · (Edited)
Yes, Open or Short is the C1200 error and you are completely right. I With back probing I might rule out just open but let's see.

I found the connector on the aliexpress and will be ordering that to inspect it and finally to try to depin my own:

I will work on it this week and post back.

Thanks a lot (y)

EDIT:

For a future reader, I found manual how to depin this harness:

Essentially this is the step 1:
Rectangle Font Parallel Diagram Line art


Step 2:
Black Rectangle Slope Font Line
 

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Excellent. Great find on that connector literature. And from that document you posted, there is a part number for the contacts inside. The part number for the small contact (.060) is 900293. And I found it is available for purchase, at least in the US.

You probably already found it already, but here's a datasheet for the contact:
900293 datasheet

Good luck with the continued investigation!
 

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Discussion Starter · #34 ·
Been quiet for a few days and that is because E37 is one hell of a connector to depin but finally I did it and transferred all the pins to a used connector I managed to grab.

Then I connected sensor directly through a wire to a new harness/connector with EXACT pins, meaning I've overridden the whole factory wiring for FL sensor and used other harness/connector to do so with stock pins that are in place of a factory wiring for 1 & 2.
I believe that is as direct as it gets.... unfortunately.

RESULT:
FL sensor Open/Short - intermittent as it was, absolutely no change whatsoever.
Did clear it and driven a lot. It just comes back, goes off, comes back etc. no change to previous behavior.
So that leaves me once again with conclusion that my HECU is done.

Will report once again when I find and replace the HECU to save a whole lot of a trouble to a future reader.

Thanks :)
 

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Wow. I'm still reluctant to give up on a solution that does not implicate the insides of the HECU, but I'm pretty much out of ideas.

So I would expect that there is some sort of PC board inside the assembly with all the electronics mounted on it. The question is "how modular is the design"? I believe there is a motor, a pump, and a bunch of solenoid valves. But do those parts plug into the PCB in some way, or are they directly soldered to the board?

In other words... It would be nice to be able to take the electronic board out without disturbing the hydraulics. I have no idea.

I admire the depth of troubleshooting you are going through. Methodical and creative.
 

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Discussion Starter · #36 ·
Dear Tiberius, your help was awesome, but really multiple fingers pointing towards ABS HECU and there is no way around it....
I ordered a used HECU and hope that that one works.

Unfortunately, it can't be removed without bleeding the system etc. because the bracket that holds it in place is designed that way.
Looks to me that designer intentionally did that so ABS unit has to be replaced in whole and not just the electronic part.

Once the whole unit is out, there is only 4 screws holding it on, so that should be easy.

This is how it looks like and bracket doesn't let you move it more than 1/4 inch and that is to little to jiggle it out:
Bumper Wood Auto part Automotive exterior Composite material


Thanks again and I will be back once I replace the HECU.
 

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Unfortunately, it can't be removed without bleeding the system etc. because the bracket that holds it in place is designed that way.
I was looking at my car recently to try to help with your issue and I saw what you were talking about with the mounting bracket being in the way.

I was thinking that you might be able to take the mounting bracket off the HECU, but leave the HECU in the car hanging from the hydraulic lines. With the bracket out of the way, you should have enough room to get the cover off. Of course, I haven't tried to do this, but it looked possible. I also don't know how heavy the HECU is, so you might need to support the HECU from underneath while working on it.

I'll take another look and see if that really seems like it could work.
 

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Discussion Starter · #38 ·
Dear Tiberius, I'd like to buy you a beer for all the help you provided.
You are indeed a great person my friend :)

ABS HECU replaced and no more problems....

The moral of the story is HECUs actually can go bad and if it looks like a fish and swims like a fish, it might just be a fish.

Hope this troubleshooting actually helps somebody in the future! :)
 

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Well Mladen my friend, That is fantastic!!

However, from where I stand, it looks like my major contribution was that I just delayed you fixing what you already suspected. You already thought it was the HECU and I came along and suggested running all these other tests that in the end brought you back to where you were a month earlier! Haha!

Seriously though, I'm very happy you got to the bottom of it, and I'm thrilled to have been a part of that process.

So couple of questions for closure... Were you able to replace just the electronics portion without having to open up the hydraulics wet section? Or did you have to replace the whole module? And can you post some good close-up pics of the electronics board? Just so I can have a peek at it?

Congrats, and I will have my beer tonight and toast you and your success! I will have a Pilsner Urquell tonight! :)(y)
 
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