2004 Strange Servo ABS issue

Hello all,

Firstly, I have taken a look through the many posts about the ABS system using the search feature and i cant find any answers the same as mine, also ive asked in the FB group and Google cant match my fault so here goes......

Thank you in advance in reading this, Ive joined the forum today after a few recommendations from the FB GS group.

For my history, im a very competent car mechanic with comprehensive mechanical/electrical and diagnostic skills so I will (hopefully) understand your suggestions etc for this post

My bike is a 2004 R1200GS, 25000 miles with servo ABS. I brought it last year, rode it 350 miles home and parked it up, thats where it stayed until this Virus put us on lockdown so I decided I will dedicate the time to it and get it in operation again for the good weather. The battery (15 months old) was completely flat obviously so i put it on a recondition cycle on my c-tek charger and within a day it was ready to go.
The bike cranked over perfectly for a few seconds and sprang into life.

The ABS lights where flashing as usual until its ridden to 6mph (or whatever it is) but this time they didnt turn off so after riding it for 1 minute i returned back home to double check the obvious things. Everything looked ok, brake light works on front and rear levers but i noticed that if the bike was turned off and IGN on, i could pull the front brake lever and the servo does NOT operate but the brake light does. If I push the rear brake pedal the servo and brake light DO operate but when i release the pedal, the light goes out but the servo doesnt. The servo will run continulously until the IGN is turned off.
Once the rear brake has been pressed to activate the servo, the servo sounds perfectly normal when running and if the front or rear brakes are used, the sound of the servo changes in pitch as it always does. I disconnected the battery for a couple of hours and made sure it was fully charged once more (which it was) then connected it all back up but it was still the same.

I decided to take the bike for a little ride and see if it had any characteristics - I rode it for about 5 miles with the lights flashing and everything felt fine for the first half, I found some gravel and slammed the brakes on 1 at a time and the ABS does work for both wheels.
On the way back i noticed as i pushed either brake, the servo assistance was 'coming and going' which made for very interesting stopping distances! It sounded as if i was releasing the brake then reapplying it but i was applying a constant pressure.

Now, I have a Snap-On diagnostic tool for the cars that I work on but nothing for bikes so i called my local motorbike shop who said they do have the diagnostic tool to read the ABS on this bike and i could bring it to them to read the codes for me. (as i always tell everyone - "plug in>diagnose>repair") Their diagnostic scanner said there was no codes stored. This completely baffles me as if theres a light flashing and the system is obviously not working properly, there should be a code to tell you whats wrong with it

They suggested to me to bleed the brake system through as the have seen this kind of issue with Ducati's and a bleed sorts it out so I brought it home, took the tank off and bled the system (including the 6 nipples on the abs unit) as per a workshop manual i found online. Nope, still the same

I then got a wiring diagram for the bike and started investigating the system manually, the brake levers are connected to the ZFE control module and the wiring is fine to and from them with everything working as it should, the fluid level switches on te abs pump are connected to the ABS control module, they are working ok. The wheel speed sensors obviously work as the ABS works from my earlier test ride. All the powers and Grounds are ok, I am getting CAN signal to the ZFE and ABS modules, the CAN is 60 ohms, the CAN voltages are ok and i put my oscilloscope on the CAN and the signals look ok also.

At this point im running out of ideas

So now my thoughts are -
* Its a servo/electronic issue (not ABS as this works although i know its the same system)
* The servo does not operate initially from the front brake lever but the signals are ok to the ZFE module
* The servo does operate initially from the rear brake lever and the signals are ok to the ZFE module
* fluids have been completely changed with fresh DOT 4 including all 8 bleed nipples, as per the service manual i downloaded.
* The brake lever signals go to the ZFE module then the servo operates via CAN instruction

Im wondering if the bike shop only scanned the ABS module but theres an existing code in the ZFE which may not have been scanned? If the ZFE is having a tantrum due to the voltage decaying to 0 as its been left for so long then may not have liked the bike being charged up (I did not disconnect the battery when charging, i know i should have)

I do not want to jump in and remove the ABS system, im looking for definite answer what the fault is, if its the servo/abs unit itself then i will have to remove it or get it repaired but its the diagnostics im struggling with and finding out whats wrong with it.

My Snap-On diagnostics tool will read all BMW cars, I have ordered a lead (1 weeks away) to allow my 16 pin OBD connector to plug into the motorbike but i dont know if it will be able to read it or not. It depends on if BMW gave motorbike and car ABS systems the same CAN address and if i can pull the codes from it once ive found the correct protocol.


I would really appreciate for someone to give me some more things to check / suggestions / experience etc as to if you have heard of this fault before? and where to proceed to next? I really dont want to rip it out until its confirmed as 'dead'. Bikes location is Clacton on sea, Essex.

Thank you all so much for your time in reading this (if youve got this far). I'll post a few pictures below of what ive done/ found etc

Kindest regards & stay safe!

Mark

Here is a link for a few pictures of what ive been up to. I hope it works as i can not work out how to use the Attach Image function with a dropbox link.

https://www.dropbox.com/sh/njc7dr0sn0nqe2s/AADqgU9ILVwx4uOreBQxDAc2a?dl=0

the ABS on all BMW cars and bikes is designed to die....

you have the early one that is even less reliable and its very rare people seem to repair... the really bad news is this module is stupid money. so most disable it.... there's another post just around this one

this repair place doesn't list a repair for the early one only the later type here https://www.ecutesting.com/product-catalogue/bmw/r1200gs/abs-pump-ecumodule-combined/

Hi,

For a relatively cheap diagnostic system I use the motoscan ap see https://www.motoscan.de/ (use google translate to convert web site to English) the ap is used in conjunction with a bluetooth OBDLink LX reader and adaptor cable. May help with your diagnostic requirements.
Good luck.

Ian

ianm00 said:

Hi,

For a relatively cheap diagnostic system I use the motoscan ap see https://www.motoscan.de/ (use google translate to convert web site to English) the ap is used in conjunction with a bluetooth OBDLink LX reader and adaptor cable. May help with your diagnostic requirements.
Good luck.

Ian

Click to expand...

Thank you very much Ian, i have an ELM327 lead and awaiting the OBD conector lead to turn up. Just got to find an android phone for it to run on now

Mark

Botus,

Thank you. I have used AC Tronics before, they was very good.

They have some ABS systems listed, i may call them but would rather diagnostics first to narrow down the fault rather than immediately point the finger (at the most unreliable part admittedly)

https://www.actronics.co.uk/abs-ecu/ate-mk61-bmw

Mark

The old 04 servo units are a ticking time bomb

Its not IF your unit fails It is When your unit fails

Its dead simple the electro hydraulics/pressure sensors are fucked !!

Remove the ABS unit carefully from the bike and Junk the ABS pipework

Detach ABS ECU from ABS Block and Seal it up some way

Reconnect to the loom and secure it in the bike

Fill the now standard brake pipes and bleed them through the callipers as you normally would

Refit Tank being careful to not dislodge cables from the junction box at the left of tank by the airbox

And that's it

Well You may want to junk the rear pads and fit Ferodo FDB2035P Platinum pads because there will be NAFF all feel to that back pedal

And you will want to remove and separate the display and paint the ABS LED s they get really annoying after a while

N.B. You do NOT need to cut any wires with this method!! Just refit the ABS ECU back in the loom (obviously sealed up from the elements ) and paint out the ABS LEDS and sort brake pipes and fluid (and maybe the softer pads in the rear)

Thanks Dr, that makes sense. I was thinking it’s something electronic that activates a pressurised system.

I’d like to understand the system more to be a able to prove it’s that 100% and then I’d be happy to remove it but it’s going to be an integral part of the pump unit so I can’t.

I still struggle to accept that the servo doesn’t start to with the front brake lever but does with the rear. Also that there was no fault codes stored. I don’t want to doubt the technicians ability to use the tool but I can’t help but wonder......

Mark


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Morning Mark,


To add some more info to your project

An ELM327 unit i unlikely to work,

iv'e already tried, there are numerous versions of the ELM327 interface -

Some work (albeit in a limited fashion) and others plain old dont.

You also need a 10 pin round to OBDII male adapter as well if i recall.

Motoscan or GS911 are the only units that work,

( it's a bit like Saab & GM diagnostic kit, some work but you need the proper ones to to do anything correctly )

Ad DR F has said the early ABS/servo units are a ticking timebomb. one they go off thats it.

To give you some ideas of where your going costs wise

A new unit fitted & flushed from a main dealer will not see any change out of £1200+

if you want to do it yourself you wont see much change out of £800+ for a new unit

And if i recall you need to prime / flush the system using diagnostic kit (say GS911 ) from £100 - £360

Even if you find and fix your fault, the random time generator has been triggered

and it's only a matter of time before it, or another part of it fails.


Another more pragmatic way to look at it would be

As your a car mech, if a customer dropped a car in costing about 2K for an unknown intermittent fault diagnosis & fix,

at what stage would you say it's uneconomical to work on / fix, or if it was your car , at what stage would you say to the garage, it's cost

to much to carry on looking at it?

If your absolutely insistent they you want it fixed, i think there are a couple of places that do a repair,

but again your looking at £400 odd, but bear in mind your fitting a refurbed part into an old system.

a bit like replacing your boiler at home, and not doing a power flush - These units are so fussy on fluid and fluid changes..

To servoectomise is about £30 in parts and about a half day to do.

I dont know anyone who has done a servoectomy & said i want to go back to the old system


Welcome aboard BTW

Thanks Santa for your comprehensive reply, very useful!

As it’s servo assisted, what happens when the system is removed? There will be no servo and I know when this servo stops, it’s a bit scary!!!

I understand there is a servo abs system and a conventional abs system used on the later bikes , I understand with the latter system but what does no servo feel like?

Thanks again

Mark.


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Mark_C0 said:

Thanks Santa for your comprehensive reply, very useful!

As it’s servo assisted, what happens when the system is removed? There will be no servo and I know when this servo stops, it’s a bit scary!!!

I understand there is a servo abs system and a conventional abs system used on the later bikes , I understand with the latter system but what does no servo feel like?

Thanks again

Mark.


Sent from my iPhone using Tapatalk

Click to expand...

Hi Mark,

I recently had the same problem with my bike, I have a very similar background to you (vehicle technician, turned engineer at Ford)

I fully removed the ABS pump and module and coverted the wiring to Non-ABS spec.

The brakes without the servo are fantastic. I would highly recommend it as the way to go.

I shall post below the quick write up I did on the process.

Thanks Luke

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LukeBarton said:

Hi Mark,

I recently had the same problem with my bike, I have a very similar background to you (vehicle technician, turned engineer at Ford)

I fully removed the ABS pump and module and coverted the wiring to Non-ABS spec.

The brakes without the servo are fantastic. I would highly recommend it as the way to go.

I shall post below the quick write up I did on the process.

Thanks Luke

Sent from my SM-G965F using Tapatalk

Click to expand...

Firstly, apologies for the delay in posting this, but here is my take on removing the ABS unit (and module) from my own 2005 R1200GS. This is not a guide as such just a detail of what I have done to my own bike.

So, a quick backstory, I saw a low mileage, very nice condition BUT VERY CHEAP GS for sale earlier this year, further investigation revealed it was cheap due to it having an ABS fault. I am a Diagnostic Engineer for a well-known car manufacturer so figured I should be able to fix it myself and that the bike was worth a risk. So, I ordered the bike without seeing it and had it delivered.

My original intentions were to strip and attempt to repair the ABS pump, but the more I looked into it and found out the multitude of problems these units can have the more I edged towards removing the servo and ABS all together.

I planned to carry out the ABS pump removal as many others have and to leave the control module on the bike to keep the speedo operating, just blanking out the warning lights.

For the front brake hydraulics, I decided not to fit a fluid loop to the front brake manifold as most do. Instead opting for a Goodrich build-a-hose between the Front brake master cylinder and the bottom fork bridge clamp, I used a P-clip to secure the hose at the attachment point usually used by the manifold, which gave me a very nice hose routing. (Hopefully a picture of this is attached?)

For the rear brake hydraulics, I opted to order an original rigid hose for a NON-ABS bike from motorworks for ease and a factory look finish.

The brakes bled out easily and work very well indeed.

I then went about blanking the warning lights in the instrument cluster, however I soon realised that I would not be happy with this solution.

The reason for this was because the red LED’s for the warning triangle light take precedence over the yellow ones and due to the ABS fault on my bike the RED warning triangle was constantly illuminated, meaning I would never see the yellow triangle for faults such as bulbs or fuel level.

I then set about acquiring the wiring diagrams for both ABS and NON-ABS variants, which confirmed what I had read around the speedo being controlled by the ZFE module on NON-ABS bikes. It appeared, all that was required was to connect the rear wheel speed sensor to the ZFE and programme the bikes modules for NON-ABS. Simple!

The details of this are as below, I’ll start from the point I had already removed the ABS PUMP and module. With regards to the programming I purchased the Motoscan app and a decent Bluetooth OBD dongle with an adaptor lead, I have heard very mixed reviews about the Motoscan software, but for me it worked perfectly.

The first thing I did was to disassemble the ZFE module multiplug to identify the pin types I required for the new connections (I have managed to source the correct pins and have some spares, so if anybody requires some let me know) (picture of pins should be attached?).

Once I had the pins the wiring modification was very straight forward.

Firstly, I crimped 2 pins to around 800mm of 0.5mm2 wire each. I then fitted the pins to the ZFE module multiplug. One to PIN 13 and the other to PIN 51 (these can be identified by small numbers embossed in the plug itself)

I then ran my new wires alongside the original loom down to the vicinity of the ABS module.

Next, I cut the wires that connected the rear wheel speed sensor to the back of the now redundant ABS multiplug (PINS 6 & 8), I did this one at a time so as not to get things muddled up.

The wire that used to connect to pin 6 of the ABS module was soldered to my new wire connected to PIN 13 from the ZFE and insulated with heatshrink. The same was done to connect the second wire (previously to PIN 8 of the ABS module) to my new wire connected to PIN 51 of the ZFE.

This is all of the wiring modifications required and it would have been ample to insulate the old ABS connector and tape/cable tie it away somewhere….. I opted to remove it completely as I never have any intention of returning the bike back to ABS.

I then used the Motoscan app to recode the bike to non ABS. It is important to note that I had to recode the ZFE, ABS, Engine ECU and Instrument cluster, they all had a drop down with ABS fitted YES/NO. I found when I only coded one or two of the modules they resorted back to ABS with the next ignition cycle. I presume they do some kind of “handshake” on boot up and ABS fitted takes precedence.

Once recoded I keyed the bike on and spun the rear wheel and found the speedo to be working as hoped! I was able to un “blank” the warning lights in my instrument cluster and now all of the telltales illuminate and go off again when switching on the ignition just as a NON ABS bike would. I have since also removed the front ABS sensor and sensor ring..... I may remove the ABS disable button one day to totally finish the job!

Apologies for the rambling document and that I didn't take any (useful) pictures at the time.

Hopefully, if you have made it this far, you may have found it interesting/helpful.

If anyone has any questions or are attempting to do the same conversion to their bike and want some advice, let me know.

All the best

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Mark_C0 said:

Thanks Santa for your comprehensive reply, very useful!

As it’s servo assisted, what happens when the system is removed? There will be no servo and I know when this servo stops, it’s a bit scary!!!

I understand there is a servo abs system and a conventional abs system used on the later bikes , I understand with the latter system but what does no servo feel like?

Thanks again

Mark.


Sent from my iPhone using Tapatalk

Click to expand...

What does it feel like

like normal brakes (I've never had servo assisted so cant say, but it's like any bike pull the brake it will stop. The harder you pull the brake the quicker it will stop)

I-ABS generation 1 was fitted until 08/06 I-Abs Generation 2 was fitted 08/06 on

https://www.realoem.com/bmw/enUS/partgrp?id=0307-EUR-04-2006-K25-BMW-R_1200_GS_04_0307,0317_&mg=34 shows the difference

Mark_C0 said:

Thanks Santa for your comprehensive reply, very useful!

As it’s servo assisted, what happens when the system is removed? There will be no servo and I know when this servo stops, it’s a bit scary!!!

I understand there is a servo abs system and a conventional abs system used on the later bikes , I understand with the latter system but what does no servo feel like?

Thanks again

Mark.


Sent from my iPhone using Tapatalk

Click to expand...

I have just removed the servo/ABS from my R1150RS
Lovely feel on the front brake, servo not missed at all

I found the rear brake to be very harsh, almost an on/off switch. Originally Servo/ABS was a cost option, and BMW fitted different rear master cylinders for non ABS, and ABS bikes. The ABS one has 14.29mm bore, the non ABS 12mm

Got one from Motorworks, s/h £40, and now the rear brake is great

Mark_C0 said:

so i called my local motorbike shop who said they do have the diagnostic tool to read the ABS on this bike and i could bring it to them to read the codes for me. (as i always tell everyone - "plug in>diagnose>repair") Their diagnostic scanner said there was no codes stored.

Click to expand...

The devil is in the detail...... what diagnostic tool did they use ? the GS911 will give you detailed information regarding pressure and also enable tests to be preformed to check pressure on front and rear and allow manual abs/servo testing via a laptop.

LukeBarton said:

Hi Mark,

I recently had the same problem with my bike, I have a very similar background to you (vehicle technician, turned engineer at Ford)

I fully removed the ABS pump and module and coverted the wiring to Non-ABS spec.

The brakes without the servo are fantastic. I would highly recommend it as the way to go.

I shall post below the quick write up I did on the process.

Thanks Luke

Sent from my SM-G965F using Tapatalk

Click to expand...

@ Luke - what a small world - im FMC DTC too, i can see your CDSID. Im a G7 PT NVH Eng

Ive just read your comprehensive reply, thank you very much for taking the time to write that! It sounds like this is the exact thing i am going to have to do. I can see the modules on the CAN and thought id never be able to reprogram these without specialist equipment but youve found a way around that. My OBD leads are all USB so i was just about to buy a BT version so i can plug it into the convertor lead to the BMW. Is yours a fancy one or just a cheap £10 ebay one? On my USB one i can switch between MS/HS CAN and im assuming the GS just needs the MS @ 125,000kb/s as there would be no need for a HS on a bike.

I noticed also about the wheel speed sensors going to the ZFE on non ABS. Im guessing the ABS module is not a terminating node? If it was i can just add the resistor as required.

later on i will research the parts needed that you describe and look at going down that route.

Thank you very much for your reply again, Im sure one day we shall cross paths

Mark

Ajay said:

I have just removed the servo/ABS from my R1150RS
I found the rear brake to be very harsh, almost an on/off switch. Originally Servo/ABS was a cost option, and BMW fitted different rear master cylinders for non ABS, and ABS bikes. The ABS one has 14.29mm bore, the non ABS 12mm

Got one from Motorworks, s/h £40, and now the rear brake is great

Click to expand...

Thanks Ajay! this is great info!

Santa - I was worried that if i remove the servo the brake would constantly feel like when my surrent servo stops working - SCARY! I assumed the master cylinders would be different between the ABS/non ABS systems as Ajay clarified.
I would have hated to reluctantly removed the ABS/Servo to have really heavy brakes that required loads of force to operate and spoil the bike.

Thanks again everyone , this is why i love a forum. on the FB group i couldnt get any answers except "remove the system"

Mark

Mark_C0 said:

Thanks Ajay! this is great info!

Santa - I was worried that if i remove the servo the brake would constantly feel like when my surrent servo stops working - SCARY! I assumed the master cylinders would be different between the ABS/non ABS systems as Ajay clarified.
I would have hated to reluctantly removed the ABS/Servo to have really heavy brakes that required loads of force to operate and spoil the bike.

Thanks again everyone , this is why i love a forum. on the FB group i couldnt get any answers except "remove the system"

Mark

Click to expand...

TBH i never gave it any thought,

I bought the bike and rode it home, it stopped as i asked. I never got into a postion where i thought F*ck no brakes

I've locked the back end once when i stamped on the pedal, learnt not to do that and adjusted accordingly ...

For me, the best way to sum it up would be to say,

if you've had to brake just using residual braking, thats all your going to get until you fix it or remove it

Thanks Santa


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Hi All,

Been reading this with interest as I am too in the same boat.

My issue is that after fiiting the rear subframe back to complete some other work I bled the brakes via the servo but after getting that sorted when I apply preasure to the rear brake pedal one of the brake lines pops out of the servo. Done this 3 times now, twice while riding.

Rather than try and sort the "time bomb" out I am thinking it might be easier to remove it.

What is the opinion on letting the insurance know, because mine is due (sods law)

Is it best to get the kit from Motorworks to sort the pipework out?

Cheers