Abs light

Ask for and share advice on using the PicoScope kit to fix vehicles here.
Emanuele.Vag
Newbie
Posts: 8
Joined: Sun Feb 25, 2018 3:18 pm

Abs light

Post by Emanuele.Vag »

Hi everyone
I have a problem with a golf 6 20 tdi engine code cbab, the car at 15 kmh turn on the abs warning light, the error code 01130 appears in the diagnostic, i delete it and the car and the fault does not appear until i restart the car.
I checked all power supply, ground , can l-h and the four speed sensors with connected and disconnected connector i found everything ok.
When the car is raised on the bridge simulating the gear, the warning light doesnot come on.
So i decided tu plug in the picoscope and check what was going on, i checked the four speed sensors, i noticed that the 4 speed sensor at 15 kmh are showing an anomalous signal and then return normal.
So i checked a speed sensor together with the power supplies and the ground end found something strange in the ground.
What could have happened inside the abs module.
Ch blue speed sensor ch red power supply ch green ground
Attachments
abs module golf 6.png
abs module golf 6.png

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 830
Joined: Sun Aug 25, 2013 7:22 am

Re: Abs light

Post by Steve Smith »

Hello and thank you for the post.

Looking at your capture, this would appear to be interruption of the ABS speed signal when measured using voltage. (This is not necessarily a fault)

If you measure the ABS sensor current flow instead of the voltage, the signal is near immune to the operation of the ABS system

At 15 km/h (approx.) the ABS system is carrying out a pump/actuation test which maybe felt or heard by the customer if the road surface is smooth & the cabin is quiet

I have seen this event numerous times when measuring ABS sensor voltage and here is one such example

You mentioned in your post that this effect can be seen in all four sensors at approx. 15 km/h and this fits with the above self-test mentioned above.

The inrush current into the ABS pump will most certainly (momentarily) pull down on the sensor supply voltage and result in some volt drop on the earth return (seen on channel C)

From what I can see, at this stage I would focus on the description of Fault Code 01130 along with the detection condition

I hope this helps, take care…..Steve

Emanuele.Vag
Newbie
Posts: 8
Joined: Sun Feb 25, 2018 3:18 pm

Re: Abs light

Post by Emanuele.Vag »

Thanks for the reply.
Could it be too high a current during pump activation? the fact that the error occurs at the exact moment when the pump is activated makes me think that the problem is there.
I will try to check the current in that time interval which current range could I expect?
Attachments
Screenshot_20200428-232130_Chrome.jpg

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 830
Joined: Sun Aug 25, 2013 7:22 am

Re: Abs light

Post by Steve Smith »

Hello and thank you for the feedback
I assume from the description “ABS Operation: Implausible Signal” this is referring to Speed Signals?

If so, I would use 4 x Scope channels to capture 4 x wheel speed signals over a slow time frame as in the Case Study link above.
We need to capture the operation/ output of all sensors from 0 km/h up to and just after the generation of the fault code (approx. 25 km/h)
We could then plot the frequencies of these signals as they should be perfectly matched when driving in a straight line.
Using Speed Sensor current would be ideal rather than voltage but of course this requires 4 clamps (or 1 clamp and 4 road tests)

There is a very interesting line in Possible Causes “Modifications/Retrofits”
Could we confirm wheel and tyre are the specified diameter, tyre configuration/circumference are the same and check for any recent wheel bearing replacements
All the above assumes “Implausible Signal” refers to wheel speed.

Regarding ABS pump operation we have 3 scenarios
1. The ABS pump operation is part of the self-test.
2. The ABS pump is operating due to speed signal “drop” and wheel lock is assumed
3. The ABS pump is operating due to circuit or control errors
Looking at the peak inrush current with the Subaru case study we have 80 A with over 30 A when running (Hence the volt-drop in the ABS circuit)
N.B There was no error with the Subaru ABS pump or circuit

I hope this helps, take care……Steve

Emanuele.Vag
Newbie
Posts: 8
Joined: Sun Feb 25, 2018 3:18 pm

Re: Abs light

Post by Emanuele.Vag »

Hello to everyone today i restarted working on golf again, i checked the front speed sensors together then the rear ones.
The front ones seem to have the same frequency while the rear ones seem to differ from each other.
Now i have a problem i am new to the picoscope i m not familiar whit math channels.
Attachments
ruote posteriori.png
sensore velocità anteriori.psdata
(27.87 MiB) Downloaded 52 times

Emanuele.Vag
Newbie
Posts: 8
Joined: Sun Feb 25, 2018 3:18 pm

Re: Abs light

Post by Emanuele.Vag »

I made another capture of the rear wheels and they seem to have the same frequency
Attachments
ruote posteriori.jpg

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 830
Joined: Sun Aug 25, 2013 7:22 am

Re: Abs light

Post by Steve Smith »

Hello and thank you for the feedback

Could you confirm the fault code generated is referring to a wheel speed signal?

There is a very interesting line in Possible Causes “Modifications/Retrofits”
Could we confirm wheel and tyre are the specified diameter, tyre configuration/circumference are the same and check for any recent wheel bearing replacements
All the above assumes “Implausible Signal” refers to wheel speed.

I have opened your capture using PS6 so as to check if you have a 4-channel scope (which is perfect)
I cannot see a frequency concern when the signals are stable, however they may be out of phase but this is not an issue.
PS6
PS6
We need to use 4 x Scope channels to capture 4 x wheel speed signals over a slow time frame as in the Case Study link above.

We need to capture the operation/ output of all sensors from 0 km/h up to and just after the generation of the fault code (approx. 25 km/h)

It would appear that AC coupling is not helping here when the ABS pump operates

This is what we are trying to achieve……
PS7
PS7
The vehicle above has a faulty ABS pick up ring within one of the wheel bearings and you can see how the frequency changes momentarily once per revolution. This results in activation of the ABS pump in response to the abrupt frequency change from a single wheel.

If we could repeat the above test (DC Coupled) this will help, we can then filter to improve the frequency calculation using math.

Ideally 4 x current clamps would be perfect but I understand this is not always possible

Please please do not go to the lengths above if your code is not referring to ABS speed signals

I hope this helps take care…….Steve

Emanuele.Vag
Newbie
Posts: 8
Joined: Sun Feb 25, 2018 3:18 pm

Re: Abs light

Post by Emanuele.Vag »

Hi Steve
I m not sure that it refers to speed sensors, looking on the internet you can find only that error description.
I made another DC acquisition of all 4 sensors but i can t convert them to frequency.

Emanuele.Vag
Newbie
Posts: 8
Joined: Sun Feb 25, 2018 3:18 pm

Re: Abs light

Post by Emanuele.Vag »

Unfortunately the time is very low, i managed to apply the mathchannel but only on ps6 this is the result.
I will try again to make another capture to see if that peak on channel D repeats.
Attachments
Sensori ultimo.psdata
(20.03 MiB) Downloaded 47 times

Emanuele.Vag
Newbie
Posts: 8
Joined: Sun Feb 25, 2018 3:18 pm

Re: Abs light

Post by Emanuele.Vag »

Another capture
Attachments
20200502-0001.psdata
sensor frequency
(2.35 MiB) Downloaded 51 times

Post Reply