GS-911 User Forum

General Category => Technical => Common trouble codes or issues with known solutions => Topic started by: kobus on April 19, 2013, 08:47:41 AM

Title: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: kobus on April 19, 2013, 08:47:41 AM
Symptom:
ABS Light on, only residual braking left

Solution:
Try the following in order:


Do a sensor drift test.
If you get an error: "Offset values of internal pressure sensors not OK" it usually means you have to replace the control unit because the sensors stopped working.

Prevention:
Properly bleed the brakes every year and use the ABS bleed test to move the fluid in the ABS module itself to prevent corrosion and damage of the sensors.
Do not use a high pressure cleaner!
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on May 16, 2013, 06:01:50 PM
A possible fix for this problem

These are your 2 pressure relief valves, the Yellow for the front and Red for the rear circuits.
(http://i44.tinypic.com/219dwz4.jpg)

Sometimes these valves get stuck, thus not allowing the pressure to release. 

Firstly remove the rubber boot around the base of the valve.  They are rather tight and will need a little force to get them off.  They are rubber however so will come off without damage.
(http://i41.tinypic.com/sls41w.jpg)

Next, remove the valve itself, using a 26mm wrench.  This is what it looks like.
(http://i42.tinypic.com/2zykaj8.jpg)

Make sure that the plunger on the end travels up and down freely, without getting stuck.  It is spring loaded with a rather heavy spring, but you should be able to depress it against the spring pressure by hand.
(http://i43.tinypic.com/bdqnfk.jpg)

This is the movement you should have.
(http://i39.tinypic.com/2ymtyld.jpg)

Push the plunger in a good few times to make sure it is moving smoothly.  Replace it, bleed the pump (in the correct sequence) and wheel circuits and test again.  You can even swap the 2 valves around to see whether the problem shifts to the front wheel.

I have had a number of problems with pressure and have been able to resolve most of them doing the above.  If the problem persists and moves if you swap the valves, then the valve will need to be replaced.  Unfortunately, BMW does not sell the valve loose so you will have to source those elsewhere.

Hope this helps!
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: kobus on May 17, 2013, 03:27:12 PM
Wow, thanks for this. It will help a lot of people!
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: StephanT on May 17, 2013, 03:33:48 PM
and another Karma applaud for Jughead!

+1
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Alexm1 on August 11, 2013, 07:21:37 AM
Jughead, thanks, I hope I won't need this but a clear and concise process if I do. Much appreciated.
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on August 11, 2013, 08:14:22 PM

Pleasure!
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Mission on August 13, 2013, 09:54:05 AM
I have the iABS on my 2004 K1200RS and as Jughead suggested my problem may have been the pressure relief valves but alais it was not the fix. As I have tried every other fix,  I am now back to my original suspect, the sensors ( Not the wheel speed sensors ) which are 5 volt peizo ceramic transducers under the bottom of the pump unit which drive Mosfets for front and back systems. I originally had the "rear brake circuit pressure high " and 4Hz light but now it completely random and sometimes I have both lights flashing with or without brakes. 

Does anyone know if Module Master in America does the iABS overhaul yet ?

Jim
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Alexm1 on August 16, 2013, 03:33:43 AM
Jim, I understand MM will be ready later this year. There is another repairer in Tennessee, automotive Scientific Inc.
What about jughead, does he fix to that level?
Refer to this note in I BMW.
http://www.i-bmw.com/showthread.php?t=44589
Alex.
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on August 16, 2013, 10:12:22 PM

What about jughead, does he fix to that level?
Refer to this note in I BMW.
http://www.i-bmw.com/showthread.php?t=44589
Alex.

I have honestly never had need to repair one of these pumps as they, to my mind anyway, are the better pumps to have.

I do, however, have a spare one which was given to me some time back.  I do believe that it was also replaced when it went "Faulty", but that the fault was eventually traced down to a chafed wiring harness.

I will have a look over the weekend and see what dismantling it entails.  I have also seen a huge sludge buildup in some of these pumps despite the fluid being flushed regularly.

Will report back in due course.
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on August 19, 2013, 01:31:38 PM
OK, I have been fishing around while refurbishing my spare ABS pump.

Looked like this:

(http://i44.tinypic.com/jrspqu.jpg)

Now looks like this after the strip and clean:

(http://i43.tinypic.com/rqzmdj.jpg)

(http://i39.tinypic.com/2w7pc7p.jpg)

(http://i41.tinypic.com/16ljtac.jpg)

While I was at it I came accross this sensor:

(http://i39.tinypic.com/332md10.jpg)

Made by FTE, it is a pressure transducer, and no doubt the part that results in the Pressure Errors within the pump.

Outside looks like this when removed:

(http://i44.tinypic.com/2i27i2a.jpg)

Inside looks like this:

(http://i40.tinypic.com/64e6u8.jpg)

I am at present trying to source these to test with.
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: bikecrazy5 on August 19, 2013, 09:50:10 PM
brilliant work jughead :D
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Beamietoo on October 14, 2013, 03:42:33 PM
@ Jughead,

I have see a lot of abs control modules and can say that yours is even cleaner than a new unit !
Curious what you use to achieve that result?
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on October 14, 2013, 04:03:55 PM
Bead Blasted!  ;D
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Beamietoo on October 14, 2013, 04:14:46 PM
NICE !!
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Kishon on April 20, 2015, 12:17:08 AM
Hello everyone! I am a motorcyclist from Poland and have 2005 BMW R850R. My integral ABS just break up. I am looking for information that could help me in the repair. I see that Jughead has done a great job with his pump. I'm interested in, is there a way to check this pressure transducer? Is it possible to measure the electrical resistance in order to check and, if so, does anyone know the correct value? Thanks for any help!
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: harrimansat on December 08, 2015, 08:33:03 PM
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Kishon on December 11, 2015, 01:56:34 AM
Thank you. Truth is, I am not able to perform this test. But this is no longer a problem. In my motorcycle I removed the iABS. It's probably the most sensible what you can do for BMW. ;-)
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: harrimansat on January 05, 2016, 08:35:42 PM
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: chadzilla on January 06, 2016, 06:27:20 PM
Cool pics!
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Marko123 on April 23, 2016, 02:10:50 AM
Well guys I'm getting this fault code after having a new wifi 911 kindly give me the answer but what does it mean.

Fault Codes : 1
- :
24971 : Pressure in front wheel circuit to high
Currently present : YES

Please help aaaahhahhhhhhh
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: emin8 on July 10, 2016, 09:16:13 PM
Hi
I need a pair of pressure relief valves, where can I get them, I'm so desperate as I'm having trouble getting hold of them...!!!!  HELP
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: gogy on May 10, 2017, 09:27:54 AM
hallo jughead

I am new to this forum, come from switzerland and have a gs 2006, I use a translation machine and hope it is translated correctly, my question, how did you get the valve without effort, 2. where can I get a new valve, Bmw can not cheat me, with my valve comes the brake fluid when I release the front brake, 3. I can perhaps revise it myself, the valve, and why the liquid comes out, thanks in advance for the reply, gr gogy
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: gogy on May 14, 2017, 09:02:13 PM
Someone knows maybe what you can do here, and where you can buy the valve

Sent from my SM-G925F using Tapatalk

Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on May 16, 2017, 07:09:20 AM
Hi Gogy

My apologies for the delay in replying.  I have been on holiday and only back on Friday.

Not quite sure which "valve" you are referring to.  Google translate is not good.

From the translation, you appear to have a leak somewhere.  Maybe it would help if you post a photo of the "valve" and show where it is leaking?

If it is this part:

(http://i39.tinypic.com/2ymtyld.jpg)

I can gladly send you one.  It is not new but in good working condition.

Sorry I can't be of more help, but at the moment I don't know what to help with.
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: gogy on May 16, 2017, 07:14:09 AM
this valve
It has a hole on the side, and there dripping it, I wais not why, I can sunnily translate no other except with translate 😊(https://uploads.tapatalk-cdn.com/20170516/26e85107195896cb39051c4005765ac0.jpg)(https://uploads.tapatalk-cdn.com/20170516/71ade4aefea03f8a6efff8726e5153dd.jpg)

Sent from my SM-G925F using Tapatalk

Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on May 16, 2017, 08:59:27 AM
Ah!

If you send me your details and address, I will send you one.
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: gogy on May 16, 2017, 09:11:24 AM
i sent you PM

Sent from my SM-G925F using Tapatalk

Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on May 17, 2017, 10:05:33 AM
i sent you PM

Sent from my SM-G925F using Tapatalk

Hi Gogy

Please check the addresses and tell me if they are correct and which one you would prefer.

Goran Mitic
Brugghalden 15
9300 Wittenbach
Switzerland

OR

Goran Mitic
C/O Mandy Klein
Opelstrasse 3
78467 Konstanz
Germany
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: gogy on May 17, 2017, 10:07:07 AM
switzerland ist OK, send it to swiss

Sent from my SM-G925F using Tapatalk

Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on May 17, 2017, 12:11:04 PM
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: gogy on June 23, 2017, 11:49:22 AM
hallo jughead
have you shipped it


Gesendet von meinem SM-G925F mit Tapatalk

Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: gogy on July 04, 2017, 06:17:09 AM
jughead ??

Gesendet von meinem SM-G925F mit Tapatalk

Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on July 24, 2017, 06:31:58 PM
http://aramexserver.postnet.co.za/index.php/parcel-tracker

Tracking number is PPA054163603076
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: rookiller on August 13, 2017, 01:07:37 PM
Hello and here is another FTE - Fan from Germany,

thanks for sure for the nice and logical infos of these Valve Problem.

The biggest challange, where to get one of those now, i hope someone can help me out, my GS will be off the road leagaly in Germny within the next 8 wweks.

After than is useless, or i go to pruchase the same mistake FTE Module with max just an 12 month warranty at the very nice and sooo helpful BMW Deaker.

Definitly that is not the way it should happen.

Nice sunday to all of you, and always a hand space between your Ass and the ground :-)

Markus

PS:used a R1100 GS from 1994 - sold it -- MISTAKE!
--later on a KTM 640 Enduro ~ 35.000mls around OZ & NZ, only problem the chains last not that long, and the rider... :-)
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Caesarsk on March 27, 2018, 07:54:12 PM
Hello to everyone I read this post and i have exact the same problem. I am from Greece. Can someone inform me where can i find these pressure valves? Any code or link it would be perfect. Thank you in advance

Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on March 27, 2018, 08:30:31 PM
Hello to everyone I read this post and i have exact the same problem. I am from Greece. Can someone inform me where can i find these pressure valves? Any code or link it would be perfect. Thank you in advance

Hi Ceasarsk, and welcome.

What are the pressure readings you are getting?

If you look at the "Realtime Values" there will be 4 readings.
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Caesarsk on March 27, 2018, 08:37:20 PM
Unfortunately the only Message i've got is "Rear Break Low Pressure" on BMW Diagnostic Program
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Caesarsk on March 27, 2018, 08:41:13 PM
Except all other symptoms i read in this post when i press rear brake, i can't hear ABS pump motor run
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on March 28, 2018, 06:39:08 AM
Except all other symptoms i read in this post when i press rear brake, i can't hear ABS pump motor run

If the pressure is low in either the control circuit or the wheel circuit, the pump will not run.  Your problem is this sensor
(http://i40.tinypic.com/64e6u8.jpg)

If it is the control circuit, the sensor is inside the pump.  If it is the wheel circuit, it is the sensor on the outside the pump.
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: citizented on May 06, 2018, 05:02:12 PM
Hello All,

I have had issues with this ABS unit on my R1100S in the past. It was the pressure sensors, I got a second hand unit and replaced the sensors and fixed it. I also potted behind the sensor with an epoxy potting compound to give the sensor more support and prevent vibration which I thought was the cause of the failure.

I have since brought my bike back into service after the winter and all was fine, but my battery was getting tired. I charged it, started the bike and took it to work, I got an abs light at the end of my journey. When I came to go home it would not start and I got some colleagues to bump start the bike. The ABS light remained on.

I hoped with a new battery it would solve the issue, I have replaced the battery and still a fault. The GS-911 reports two faults, the front control circuit is low (0.00bar) and the rear wheel circuit is high (34.18bar). It looks to me like I have two pressure sensors faulty. I am suspicious that the original battery issue caused a fault on these pressure sensors, does this ring true to anyone else.

Has anyone found a source for these pressure sensors or do I have to find a second hand unit and hope that the sensors within it are still ok. Otherwise its the absectomy for this bike!

All the best Ed.
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Caesarsk on May 16, 2018, 08:07:32 PM
Except all other symptoms i read in this post when i press rear brake, i can't hear ABS pump motor run

If the pressure is low in either the control circuit or the wheel circuit, the pump will not run.  Your problem is this sensor
(http://i40.tinypic.com/64e6u8.jpg)

If it is the control circuit, the sensor is inside the pump.  If it is the wheel circuit, it is the sensor on the outside the pump.


Still searching for my problem. Unfortunately i've informed that my problem is the high pressure sensors and there is no spare part for this
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Jughead on May 17, 2018, 06:36:03 AM
Still searching for my problem. Unfortunately i've informed that my problem is the high pressure sensors and there is no spare part for this

Can you post/attach an Autoscan?
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Caesarsk on May 17, 2018, 09:45:22 AM
Unfortunately my mechanic doesn't give me exact results. Just Low Pressure on Rear
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: soror on October 01, 2018, 08:48:12 AM
If your problem is the high pressure sensors maybe the motor brushes in the module pump get stuck
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: mopedi on October 02, 2018, 09:46:55 AM
Hi there,
pressure too low usually means that one/both pumps do not produce enough pressure due to cloged pump or in the worst case pump is blocked, motor is burned and driver in electronics is burned too. All this comes from not changing brake fluid often ( I would say at least every 2 years or 20tkm).  The only way to fix it is to replace/clean pump, check the motor and electronic driver. Do not drive with such diagnostics readout because you may burn electronics to be unusable.

Pressure too high is another story and it usually means failed pressure sensor. They are very fragile, temperature uncompensated, electrostatic sensitive and with many possible failure modes. Unfortunatelly the only way to fix this problem is to get them from donor modulator. Do not try to remove them from the unit because 9 out of 10 will fail just by removing it from housing. With donor modulator it is another story because it is imposible to know its life time and for how long sensors will be alive.
I am performing sensor replacement for many years now with success but unfortunatelly modulator has to be machined, new sensor support made and so on (not straight forward procedure)

Silvo
Title: Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
Post by: Happyhunter on October 03, 2018, 09:53:43 PM
I have a R1200GS from 2006 with 130.000km. It has the integral ABS system witch also has too high pressure in rear brake circuit. Searching the web I found this site: https://rhelectronics.de/produkt/type-am1/ (https://rhelectronics.de/produkt/type-am1/). It is in German, but google translate can help out..

They seem to have a lot of experience with this ABS system, investigating more than 6.000 failed units over the years.

This document (also in German) describes and shows pictures of common failures and causes in this type of ABS unit.
https://rhelectronics.de/wp-content/uploads/2017/02/bmw-abs-report.pdf (https://rhelectronics.de/wp-content/uploads/2017/02/bmw-abs-report.pdf)

it seems to be a very complex unit with many failures that can occur. Reading reviews online tells that some units keep on failing after overhaul, because several components are not robust enough to last over time.

RH Electronics have developed an adapter kit to replace the ABS unit and transfer to a traditional brake system, keeping the speedometer and brake light functions. I'm thinking of this option because I had an accident recently where my front brake refused to work (ABS came in resisting to use the front brake for no obvious reason). Since the warning light was already blinking for the too high pressure in the rear system, I couldn't see the warning from the front brake. Without brakes an accident was unavoidable. Luckily my injuries were not severe, but it makes you loose trust in your safety systems. There are more cases with suddenly activating ABS in this type of system, for no obvious reason. This is why I'm thinking of removing the unit from my bike and go back to a traditional braking system.