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-   -   ABS engaging all the time (https://www.benzworld.org/forums/w220-s-class/3006857-abs-engaging-all-time.html)

oliverp 10-18-2018 05:20 PM

ABS engaging all the time
 
Hi guys

I had a similar problem before but since replacing my brakes it's been OK. Over the last couple of days I have started to get the vibration/hum through the brake pedal at low speeds. Even without my foot on the brake I can hear the pump running from time to time. It's getting really bad.

Tonight I plugged in the SDS setup and went for a drive monitoring the RPM values from the speed sensors.

The front left was always a little bit off and would be slower to react to changes in speed, but nothing substantial. After a little while the reading from this sensor would say '--' instead of a value. Only very briefly, but it was doing it.

There are no codes or errors in the ESP module though.

Do you think it's worth replacing this sensor, or is this potentially normal behaviour?

A few months ago I had an airmatic error for the front left harness on the strut. The mechanic re-seated the strut harness and ABS sensor. So I wonder if that is related?

Thanks
Oliver

noetico 10-18-2018 10:27 PM

Hi

Do you also have this no reading and humming while you make turns at low speed or experience any slight shudder at turning?

That -- reading can actually be an intermittent no signal from the sensor; if you try re-seating one more time and it doesn't work well i.e. Getting a reading all the time; inspect the wiring up to the plug point in the chassis; just to see if it's in any way loose or has damage in the wiring

If all checks; I suppose you can put in a replacement...


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Dave2302 10-18-2018 11:46 PM

/\ /\ /\ +1

oliverp 10-19-2018 05:23 AM

Thanks guys. Basically when slowing using the brakes the ABS will engage until I stop. When taking a slow turn without touching the brakes I hear the ABS pump.

Unfortunately when I put it in diagnostic mode to read the speed senors, ABS and ESP are disabled so it stops happening. I also noticed that when slowing from a very slow speed, like 10KM/h, the front left sensor will show '0' before the others.

I will try and re-seat the sensor at both ends. I'lll let you know what happens.

Thanks
Ollie

noetico 10-19-2018 08:28 AM

Quote:

Originally Posted by oliverp (Post 17583033)
Thanks guys. Basically when slowing using the brakes the ABS will engage until I stop. When taking a slow turn without touching the brakes I hear the ABS pump.

Unfortunately when I put it in diagnostic mode to read the speed senors, ABS and ESP are disabled so it stops happening. I also noticed that when slowing from a very slow speed, like 10KM/h, the front left sensor will show '0' before the others.

I will try and re-seat the sensor at both ends. I'lll let you know what happens.

Thanks
Ollie



Alright; all the best...


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oliverp 10-20-2018 09:01 AM

Hi Guys
So we cleaned the sensor, no change. I also asked that they replace the sensor and it's still the same. So the mechanic has asked to keep the car and continue looking on Monday.
I hope we can get it fixed, I am supposed to be going for a long drive on Friday!
I will update again once I hear back on Monday.
Thanks
Ollie

Dave2302 10-21-2018 01:35 AM

Hi,

You have a 1) connection at the ABS Pump, 2) Wiring from here to Wheel Arch, 3) another Connection to ABS Sensor at the Wheel Arch, 4) ABS Sensor, and 5) ABS Trigger Reluctor Ring.

It has to be 1 of those 5 items ;)

Reading this thread over, with your accurate description of the fault and works done my money is on most likely Trigger Ring next likely Sensor !!

I have had very bad experiences with Brand new "Pattern" Sensors on all makes of Cars and now I will not fit anything other than a genuine sensor / reluctor ;)

HTH,

Cheers Dave

oliverp 10-22-2018 05:50 AM

Thanks Dave, I will pass all this onto the mechanic (pretending it's my words and knowledge haha).
I should have a call with them a bit later today.
It's actually my birthday today so I am hoping for some good luck!

Thanks
Ollie

doni01 10-22-2018 09:35 AM

Quote:

Originally Posted by oliverp (Post 17585737)
Thanks Dave, I will pass all this onto the mechanic (pretending it's my words and knowledge haha).
I should have a call with them a bit later today.
It's actually my birthday today so I am hoping for some good luck!

Thanks
Ollie

Happy Birthday bud and hopefully they give you some good news :thumbsup:

oliverp 10-23-2018 02:06 PM

Thanks Doni!
Sounds like Dave was onto something. The mechanic just phoned. I was correct with it being the front left, but it's not the sensor. He says that the new and old sensors are indicating a missing tooth on the ring, but they are all present.
So it looks like this part will be replaced (not sure if this part is sold separately yet, or part of a bigger assembly). Also a CV boot is leaking so that will be fixed/replaced too.
I hope to have more progress tomorrow.
I will write another update with the final findings. The mechanic has taken photos and screenshots so I will share them too.
Thanks
Ollie


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