Author Topic: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"  (Read 88678 times)

Happyhunter

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Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
« Reply #45 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/. 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

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.

Andrew77

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Good day to all. Faced with the problem of ABS on my 2005 production k1200s, mileage 20000km. Watch the video and if there is a solution, where to see what to check, what error does the lamp indicate? There is no diagnostic equipment nearby. Thank you everyone.

schuppi

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Hi Andrew
Where to look first without any diagnostic equipment is very difficult in this case.
Here are many listings on this page: http://forum.hexcode.co.za/forum/index.php/board,22.0.html

Your fault sounds like > pressure in wheel circuit to high :(
Real time values are necessary
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Jughead

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Hi Andrew
Where to look first without any diagnostic equipment is very difficult in this case.
Here are many listings on this page: http://forum.hexcode.co.za/forum/index.php/board,22.0.html

Your fault sounds like > pressure in wheel circuit to high :(
Real time values are necessary

I concur!

Andrew77

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To understand the problem you need to connect a device for diagnostics? Did I understand you correctly? By the combination of flashing lights can not be determined?

schuppi

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Hello Andrew
for first aid without diagnostic equipment, riders manual is your friend

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Andrew77

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Hey.
This error is generated by the program MotoScan: "618B-front wheel contour". What could it be?

schuppi

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Hi Andrew

Ok. A good working diagnostic tool, as GS911, will give you this answer:

618B > 24971 > Pressure in front wheel circuit to high,
in relation to the control pressure

Check brake light switch, hand
Adjust brake light switch, hand
Check pressure in front wheel circuit
Check offset values of internal pressure sensors
Check control unit

Please use the "real time values" to read the actual functions.
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Jughead

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Hey.
This error is generated by the program MotoScan: "618B-front wheel contour". What could it be?

Maybe ask on the Motoscan forum.  This is the GS911 forum, so very difficult to determine what the error means.

Schuppi appears to be pointing in the right direction though.  Most likely a bad pressure sensor.

tpdnexus

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Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
« Reply #54 on: November 24, 2019, 06:28:49 PM »
I have the the pressure-too-high problem on an analog FTE iABS of my 2003 R1150GSA, 94,000 miles:
Random faults of the iABS appearing anywhere between 5 and 600miles after always correct initialization,
the GS911 readouts:
17438: Pressure in rear wheel circuit too high
The fault is not present now.
17182: Pressure in front wheel circuit too high
The fault is not present now.

which then caused the dreaded residual braking power during riding. Stopping, restarting
solved always the problem.

GS911 pressure sensor test, bleed test came all out okay, all 4 pressure  readings
after intializing are within the normal range posted here, of course switches replaced and tested,
Battery, electric connections, etc. Bleeding all circuits was always
done on time using the outstanding Castrol SRF DOT4. I bought the bike new, so I am maintaining
a log what has been repaired when.
The only abnormality I detected was the GS911 reporting the Battery Voltage of the iABS being
about 2V less than what the GS911 stated for the Mototronic and what I measured directly at the iABS connector.


After looking through all postings available I came across this excellent forum and
would like to thank all the inmates, especially jughead for the great work.
After exhausting all listed possible repairs (not changing the iABS unit yet)
I will try the release valve clean procedure posted by jughead.

My question is:
I have read somewhere that the FTE pressure sensors are piezo sensors?
I am working at of one of the leading advanced piezo component company, with
extensive experience, analysis, testing equipment, specialized piezo machining capabilities and
access to almost any PZT materials produced.  We are supplying custom made PZT sensors worldwide.

I would be interested in reverse engineering the FTE sensors (FTE has been acquired by Valero).
If it is a Piezo sensor, I would run it through our F&E department and trying to come up with replacements.
If any of you have broken, non functional FTE sensors, this would be a start, since we can determine
the used PZT material properties even from dead units. I would pay for shipping  ;)


Jughead

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Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
« Reply #55 on: November 25, 2019, 09:11:41 AM »
I have the the pressure-too-high problem on an analog FTE iABS of my 2003 R1150GSA, 94,000 miles:
Random faults of the iABS appearing anywhere between 5 and 600miles after always correct initialization,
the GS911 readouts:
17438: Pressure in rear wheel circuit too high
The fault is not present now.
17182: Pressure in front wheel circuit too high
The fault is not present now.

which then caused the dreaded residual braking power during riding. Stopping, restarting
solved always the problem.

GS911 pressure sensor test, bleed test came all out okay, all 4 pressure  readings
after intializing are within the normal range posted here, of course switches replaced and tested,
Battery, electric connections, etc. Bleeding all circuits was always
done on time using the outstanding Castrol SRF DOT4. I bought the bike new, so I am maintaining
a log what has been repaired when.
The only abnormality I detected was the GS911 reporting the Battery Voltage of the iABS being
about 2V less than what the GS911 stated for the Mototronic and what I measured directly at the iABS connector.


After looking through all postings available I came across this excellent forum and
would like to thank all the inmates, especially jughead for the great work.
After exhausting all listed possible repairs (not changing the iABS unit yet)
I will try the release valve clean procedure posted by jughead.

My question is:
I have read somewhere that the FTE pressure sensors are piezo sensors?
I am working at of one of the leading advanced piezo component company, with
extensive experience, analysis, testing equipment, specialized piezo machining capabilities and
access to almost any PZT materials produced.  We are supplying custom made PZT sensors worldwide.

I would be interested in reverse engineering the FTE sensors (FTE has been acquired by Valero).
If it is a Piezo sensor, I would run it through our F&E department and trying to come up with replacements.
If any of you have broken, non functional FTE sensors, this would be a start, since we can determine
the used PZT material properties even from dead units. I would pay for shipping  ;)

Thank you @tpdnexus, that would be awesome.  I do have a faulty unit I replaced last week, unfortunately with a second hand unit so anybody's guess how long it will last.  There are 2 sensors on the one mounting plate and I have marked the faulty one for future reference.  If you can get new ones manufactured, I will most certainly be placing an order.

I do actually in my scrap box have quite a number of these sensors, some with both both faulty, others with only 1 of the 2 faulty.

schuppi

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Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
« Reply #56 on: November 25, 2019, 10:50:06 AM »
"If it is a Piezo sensor"

Hello tpdnexus
No. The pressure sensors used here, are strain gauges with evaluation electronics.
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tpdnexus

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Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
« Reply #57 on: November 25, 2019, 05:25:35 PM »
Jughead: Thanks. If you can part with one of the scraps I would PM you our FEDEX account number.

Shuppi: I assume you have checked it out and it is a resistive strain gauge?
These are normally very easy to get and made by many companies,
IF they have failed and not the electronics. I guess in the case
of the FTE sensor it is a custom made layout.

Normally it is a small patch (brownish, Kapton shell) bonded to a bending material. The bending material translate
a pressure to a strain, which the strain gauge picks up. Looking at this picture of the
sensor posted here on this forum


it makes sense. Each sensor has four unshielded wires which is typical for strain gauges using a wheatstone bridge or four-wire-Ohm circuit. The principal are for example explained here https://www.omega.com/en-us/resources/wheatstone-bridge

This finding can help to determine if the sensor is really toast or it is the electronic on the board by measuring the resistance between the four wires. The white rectangular square is the bending material. Looking at jugheads picture of the broken sensor it appears to be a ceramic material? It needs to be rather stiff for the pressure it is supposed to measure.

Jughead

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Re: Integral ABS - CAN (servo brakes) "Pressure in rear/front circuit too low"
« Reply #58 on: November 26, 2019, 06:33:55 AM »
Jughead: Thanks. If you can part with one of the scraps I would PM you our FEDEX account number.


Thanks tpdnexus.  I do have 1 I can part with.  If you can forward me the details. I will ship it off to you.

Regards
Guy