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Discussion Starter · #1 · (Edited)
Hi crew,

I'm troubleshooting my ABS+TCS error for 2 months now and I'm going insane... If there is anyone willing to read trough would be great:

Hyundai Tiburon V6, 6 sp, 2003
50k miles on the clock
With Traction Control module and ABS


1. Cascade Hi-Scan pro emulator shows C1200 - FL Wheel Sensor Open/Short
2. Sensor was replaced AND error cleared - after one driving cycle AND after COLD start, C1200 comes on again
3. ABS operates if the error is not on (if ABS is not turned off by ECU) - I tried multiple panic stops and it worked
4. After 2nd or 3rd start in a short period (i.e. when the car is warm), ABS motor is heard and ABS/TCS lights go off
5. Checked:
  • wiring from ABS/TCS connector (pins 1 & 2) up to FL sensor - OK 1450 OHMS, no short with sensor disconnected, tried moving it around and still good
  • cleared error with hi-scan pro multiple times and error DOES NOT come on if the car is WARM - i.e. after 20 minutes of driving etc.
  • however, the error does come ON after cold restart (i.e. next day)
  • al fusible links check out OK

Any ideas to try next?
Thank you kindly
 

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Discussion Starter · #2 ·
  • made a FL sensor "Flight Record" on a Hi-Scan Pro emulator on a cold start:
    • Cold started the car
    • Cleared C1200 code
    • Started flight record for FL sensor and it was reading OK UNTIL
    • I made a sharp turn to the left and sensor reading goes to 0 and stays there
    • I repeat the sequence (with the car warmed up by now) and error does not come back on (it will when the car cools off)
 

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2006 Hyundai Tiburon SE
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  • made a FL sensor "Flight Record" on a Hi-Scan Pro emulator on a cold start:
    • Cold started the car
    • Cleared C1200 code
    • Started flight record for FL sensor and it was reading OK UNTIL
    • I made a sharp turn to the left and sensor reading goes to 0 and stays there
    • I repeat the sequence (with the car warmed up by now) and error does not come back on (it will when the car cools off)
The sensor is likely in good shape. Just make sure it's a Mando brand (OEM) wheel speed sensor for best results.

This indicates something is loose in the wiring or your tone ring on the axle is loose or broken. Inspect your harness for any damage between the sensor and the plastic fender lining. Check if your tone ring on the axle is loose or spinning freely. When you take a sharp left turn it is stretching the left suspension towards it's maximum travel. make sure there is enough slack in the sensor harness that it doesn't pull tight when the suspension is in full extension.
 

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Discussion Starter · #4 ·
Thanks a lot Chase for jumping in.

I'm quite confident that problem is not mechanically related as I have inspected the exciter and it was in a great shape.
Same goes for bearing, axle etc. it's all nice and tight as the car has barely broken in (50k on the clock).

The problem is most probably electrical in nature as I saw the sensor going to the 0 mph while cornering on the Cascade Hi Scan emulator (and not going off to some extent).

That points to intermittent connection either in HECU, HECU harness or wiring.

Will keep everyone updated
 

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Discussion Starter · #5 ·
Update 1:

Went for a ride with Hi-Scan emulator connected.
Used "Graph" functionality to plot FL sensor data in combination with, FR, RL and RR sensors (one at the time).
Sensor data comes perfectly in synch all the time in any FL and other sensor combo.
This is how it looks like:

Font Rectangle Parallel Electronic device Technology



All was nice and smooth until I went for a more aggressive driving and breaking.
It was still all nice and in synch but all of a sudden HI-Scan Emu "Lost Communication" and ABS and TCS came right on as well as the same old C1200 code.
To be honest I'm not sure if I bumped the connector with my knee or it lost connection on its own.
Then I cleared the codes and went again, this time more relaxed due to traffic but still was able to "push / pull" for a few times and all sensor combos worked.
Upon checking codes there was no codes.

It will come on again, no doubt about that...

Before that:
1. I tried to provoke open loop at E37 HECU harness (disconnected from HECU) and still can't do it for the love of god
2. Tried to provoke OL on the HECU pins and again, can't do it with slight pin 1 & 2 movement etc.
3. Cable FL sensor to E37 HECU is not short to a ground with all possible movements I could think up (with both sensor and HECU disconnected)
4. Grounds on the E37 HECU connector (Pins 8 & 24) are rock solid

Next, I'm looking to disassemble the E37 connector but it is quite convoluted.
Is there any sort of simple way to get female "sockets" out?
On KET connectors there is a small lip that when pushed lets the pin or socket out but on this one (CR25F006 harness) can't do it simply it seems...

Thanks for reading
 

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Discussion Starter · #6 ·
Update 2:

Finally caught the FL sensor "dropout" on chart:

Rectangle Product Purple Font Slope


And another one:

Rectangle Slope Font Screenshot Parallel



Tested the E37 harness and it is rock solid (disconnected from HECU, gives constant 1,5 kOhm to the sensor side).
Tried twisting, shaking etc. never lost a connection.
Above sensor dropouts are not driving over bumps etc. but rather first one is while stopped in the traffic light and second one during breaking (on the leveled pavement).

What to make of it all? :unsure:
 

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When you tested the E37 harness, was that end to end on each wire, or was it plugged into something and you measured from one end?
If end to end (harness completely unplugged) resistense values should be about "0" ohms.
 

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Discussion Starter · #8 ·
Hey @Charlie-III, thanks for taking time and jumping in!

I tried all methods and both checked out OK:

1. Measuring pins 1 & 2 from Harness E37 side --WITH-- FL sensor connected
- gives 1,5 kOhms (it's a really hot day and I did some driving before)

2. Measuring pins 1 & 2 from Harness E37 side but --SHORTED-- on the sensor side (sensor disconnected)
- gives continuity with 0 Ohms

3. Measured wire by wire end to end and still 0 Ohms

4. Measured HECU connectors 1 & 2 with harness disconnected and getting huge kOhm number 50+ kOhms
- NOT getting open loop (O.L) even if I shake things

I twisted harness, wires, sensor, shaken things and it can't dropout.

All that made me rather confided that problem is on HECU side, but then again I have read through ALL ABS posts on the forum and everyone claims that ABS HECU replacement is extremely rare. Also the car is having less than 50k miles on the clock and I have it for 3 years now and never had ABS or breaks problem. Pads and rotors are less than 1Y old, fluid topped etc.

I narrowed it down to HECU or HECU-E37 Harness continuity.
The problem seems to be less frequent when the car is driven for a while i.e. has hot engine bay with potentially expanded pins or even SMD capacitors are filled etc.

Yes, I'm going insane over this :rolleyes:
 

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Discussion Starter · #9 ·
Update 3:

I made a cable to connect laptop sound card output as a sine wave generator to the ABS sensor and was capturing what ABS was reading back in Cascade.

While doing that I shaked every possible place I could access the main cable, E37 connector and harness, HECU it self, connector and cables in the wheel well etc.
and could not break the contact. Signal, as interpreted by HECU and BCM stayed nice and reactive to FREQ change on the tone generator.

Now what? Do I have any options left?

Computer Personal computer Laptop Touchpad Netbook
 

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OK, time for "off the wall" tests!
Jack up that wheel, check for bearing play using wiggle test (hands at 12 & 6 alternate which hand pushes or pulls....then 3 & 9, same thing). Should be essentially no movement.
If OK, grab a hair dryer or heavy duty hot air gun and heat the tone ring, go for about 110*F or so. This is rather warm to the touch. Go for a drive and see if the code stays off. The heat simulates you have been driving. You could also use a propane torch, but you want the tone ring warm, NOT hot.

Report back when complete.
 
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Discussion Starter · #11 ·
@ Charlie-III thanks a lot for the ideas!

1. Wheel / bearing have zero play, that was one of the first checks I did

2. Awesome idea! SO I did that with a hot air gun. Decent warming up but soon after the car started moving I got ABS motor noise and ABS/TCS lights
- being pissed off, I went to a highway and did some runs, including some hard braking (ABS OFF) ~ 15, 20 minutes, then I filled some gas and drove away home without the lights coming on

So heat most definitely influences "something" - either exciter wheel or some electronic components in ABS pump / HECU.

But if you check the pictures in the post #6 you'll notice that FL sensor just abruptly cuts off(or come on).
How would it be connected with reluctor/exciter not being close enough to sensor (thus needing heat to extend)?
A threshold voltage? But wouldn't it always cut off at the same/similar speed?

I won't e able to work on the car for the next 15 days but I'll be back after that and hopefully bring this to a closure.

Thank you :)
 

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The heat was not to expand the tone ring to close the gap to the sensor, it was to open a possible crack in it. Some are very funny about that.

You would need the ring heated to a few hundred degrees F to change the diameter much.
 

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Discussion Starter · #13 ·
Oh I see, but then again wouldn't the heat then accentuate the problem instead of curing it, in case of a crack that is?
So heating the tone ring, should then "disbalance" the front sensor readings and cause "C1201 Speed Jump" but what I have is literally sensor going offline for a brief moment then coming back. Please take a look at this picture:

Rectangle Slope Organism Line Font



"X" in the middle is the "now" line. The chart is redrawn to show past events. X travels from left to the right and draws a path (sensor red speed).
You can see me waiting on the stoplight on the right of the "X" and both sensors pickup "0 km/h".
Prior to that both sensors were in sync and everything worked (no error etc. - from cold start btw).

What you can see then to the right of FR sensor (lower) is that I start to accelerate from the stoplight and the FL sensor doesn't pick that up!
It picks it up (or comes online) on the left of the plot by "catching" up with the right sensor and then it works but ABS motor is heard and ABS shut off.

Would that really be a sign of broken tone ring? I doubt it esp. since sensors are precisely in sync when BOTH are online. It's just that FL goes randomly offline.

Urghh.... Thanks so much Charlie to taking a time, this literally drives me insane.
 

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I hate intermittent issues, you have to note what happens when. Then take issues off the list until you find it.
I would rather have something just fail, usually a lot easier to troubleshoot. Sigh.
 

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Discussion Starter · #15 ·
Agreed 100%.

In 2 weeks I'll be back with the car and angrier than ever.
Will order a small oscilloscope to observe what is the sensor putting out. Also made a cable to swap FL/FR sensors.

Thanks again for all the help and I'll report back!
 

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I made a cable to connect laptop sound card output as a sine wave generator to the ABS sensor and was capturing what ABS was reading back in Cascade.
I was having an ABS issue on a different car and spent some time driving around listening to my sensors.

Mine sounded "normal", meaning the frequency went up as the vehicle speed increased. But the problem was that the amplitude was too low for the computer to pick it up at low speeds. At higher speeds, it was fine because the VR signal was larger, but at low speeds, I would get dropouts. On that car, my ABS would kick in because the brain thought that wheel had locked up and was sliding on ice.

So did you hear anything unusual? Are the dropouts you're seeing only at low speeds? Either starting from dead stop, or when slowing down coming to a stop?
 

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Discussion Starter · #17 ·
@ Tiberius

thanks for coming in and I think you are on the right track by thinking amplitude!

Almost all dropouts are when the speed is low BUT it ain't consistent at all. I'd say 1 in 10 is a dropout on REALLY low speed.
What's worse, after the car is warm/hot it almost can't dropout.

Thus I was discussing with Charlie in previous posts about possible "pickup threshold" and thought that warming up the whole thing would extend the sensor and/or ring and make amplitude greater (peak to peak voltage).

So what did you do in the end Tiberius, how did you fix it?
 

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Glad to (try to) help. I don't have a concrete explanation as to the temperature dependence other than all electronics react to the ambient temperature in some regard. It's completely conceivable that if your FL sensor has a low output, that the detection threshold could change a small amount depending on the temperature of the sensor, the module it connects to, or both.

So for my problem, I drove around listening to the signals, and then after that, I also put a scope on it (I have a digital oscilloscope). In the end, I found that rust had built up on the cast iron knuckle and had pushed the sensor backward out of it's mounting hole a small amount. But even that small amount was enough to dramatically reduce the amplitude from the VR pickup.

On my car, the problem was in the rear. Here's a pic showing the rear sensor outputs on my car. Note that the scale of both signals is one volt per division. Meaning that (at low speed) one corner was putting out just one volt peak-to-peak, while the other corner was putting out about four peak-to-peak:
Audio equipment Electronic instrument Font Electronic engineering Engineering


Then after chipping all the rust off BOTH corners and cleaning up the mounting surfaces thoroughly, this pic shows the "after" results. Note that the scale of both signals is now FIVE volts per division. Meaning that (at low speed) both corners are now putting out about FIFTEEN volt peak-to-peak:
Product Gadget Mobile phone Telephony Communication Device


So in the end, my problem was both corners, but one of them had not yet gotten bad enough for it to drop out.

Bottom line... Pull your sensor and have a real good look at the knuckle where the sensor mounts. I was very surprised at just how small of an increase in distance between the sensor and the tone ring would decrease the signal amplitude. I mean, I knew it would cause a decrease, but it was more stark than I would have imagined.
 

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Discussion Starter · #19 ·
@ Tiberius absolutely brilliant write up. Thanks for that a lot!

I did in fact replace the problematic sensor AND used a sanding paper on the mounting knuckle. It was ne of the first things I did.

However, I'm on vacation currently and don't have access to a car, but in 10 days I'm going to hook up the scope and check voltages while driving.
Will pull sensor out once again to sand a knuckle a bit more as well.

Will report in 10 days, thanks again for all the help guys :)
 

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If there is a significant amount of rust and metallic dust in the hole where the sensor is inserted, it may interfere with the magnetic field the sensor uses to generate that signal. In your case, try thoroughly cleaning as Tiberious suggests to remove any rust or metallic dust left behind. Even if the mounting surface is clean and brings the sensor 0.5mm closer to the tone ring, there may still be other interference from rust/dust.

To give some background as to why this theory may apply to you... I work in the low voltage electrical field and in some cases I install, test and benchmark indoor DAS systems providing cellular to large buildings in Seattle. There is a type of interference we work with called PIM (Passive Intermodulation) that is caused by an assortment of metal objects within an antenna's field of operation. Even though this is primarily a problem with radio frequency signals it may also have some affect on small magnetic fields in close proximity to your ABS sensor. The biggest cause of PIM is by small metal objects within a 20-30ft radius of an indoor omni-directional antenna. More specifically rust particulates and metallic dust left behind by other contractors is a common cause and has the greatest effect on our PIM testing. Simply cleaning and vacuuming the floors fixes this in my experience. A good thorough cleaning may work in your situation.
 
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