05 servo fault

Good morning guys. Very new to this forum and to riding BMW's. Been on pans for last 8 years.

I now have 2 BMW's. 1 is the RTP and the other is an RT se. The se has an abs fault. The fault code says brake circuit front. When I investigate it further the front brake lever is not activating the brake servo motor but the rear brake is. I have tested the front micro switch and that shows a continuity when lever is out and open circuit when lever is in so assume that's ok and plus if I disconnect front brake switch the abs motor doesn't cycle on it's pre start test and the brake lights stay lit up so think that's ok. It's as if the front servo is either not getting a signal to start or has indeed failed. And ideas from the well informed would be very much appreciated.

Thank you kindly.

Good morning guys. Very new to this forum and to riding BMW's. Been on pans for last 8 years.

I now have 2 BMW's. 1 is the RTP and the other is an RT se. The se has an abs fault. The fault code says brake circuit front. When I investigate it further the front brake lever is not activating the brake servo motor but the rear brake is. I have tested the front micro switch and that shows a continuity when lever is out and open circuit when lever is in so assume that's ok and plus if I disconnect front brake switch the abs motor doesn't cycle on it's pre start test and the brake lights stay lit up so think that's ok. It's as if the front servo is either not getting a signal to start or has indeed failed. And ideas from the well informed would be very much appreciated.

 

Thank you kindly.

Morning Twinstacks

Lots of ideas but without a more exact failure code or codes to point us at something specific then that is all they are, ideas.

You mention failure CODE? Are you only getting one code or more than one? (what are you checking the codes with?)

What is the exact failure code number?

Have you checked the fluid level in the ABS controller front wheel circuit reservoir? (that reservoir is in the ABS unit under the fuel tank)

Could also be a failed pressure sensor inside the ABS unit (somewhat common).

Could be a failed or stuck servo motor.

Could be ???????

Hi mate. I am using the motoscan app on my android tablet with the correct dongle and lead. I would need to go out and put it back on to get exact code but all it says is brake circuit front and doesn't tell me anymore. This software was supposed to be as good as the gs911 but it certainly doesn't do what it says on the tin. I have bled the abs unit several times which makes no difference. The 2 other electrical plugs on the unit are level sensors and if I unplug one at a time it throws up an error code for level sensors so I think there ok. Am I correct in thinking there are 2 motors on this unit with one for the front and one for the rear? Thanks. Just got code, it says:

Trouble Codes Count 1 Trouble code 618B wheel circuit, front. Hope this helps.

Hi mate. I am using the motoscan app on my android tablet with the correct dongle and lead. I would need to go out and put it back on to get exact code but all it says is brake circuit front and doesn't tell me anymore. This software was supposed to be as good as the gs911 but it certainly doesn't do what it says on the tin. I have bled the abs unit several times which makes no difference. The 2 other electrical plugs on the unit are level sensors and if I unplug one at a time it throws up an error code for level sensors so I think there ok. Am I correct in thinking there are 2 motors on this unit with one for the front and one for the rear? Thanks

Morning Twinstacks

OK, don't bother with the motoscan app again as I'm pretty sure that the code it gives is not comparable to the BMW failure code list (hopefully the actual failure it gives is correct but there is no way to know that until the problem is found & verified)

Yes 2 motors in the (05) I-ABS system.

You can guess at it but for most failures in the motor/pump side you can't see, check, or effect the problem so that is about all you can do is guess.

Now if you had a real BMW (ie GS-911 or dealer computer) failure code then you could call Module Masters & give them the code then they can probably tell you from that what the problem is & what it takes to repair it.

The common failure on I-ABS (servo) systems in an internal pressure sensor & for the longest time there was no repair as there was no available replacement sensors. Module Masters is supposedly working on sourcing replacement sensors but I have no idea on when that will happen-- (possibly they have already found sensors).

You might call Module Masters anyhow & explain your "brake circuit front" as that m-i-g-h-t be enough for them to tell you something.

You do have a sort of option & that is to remove the ABS system, BUT!, your speedometer & brake lights/tail light are driven by the ABS system so you will not only have to re-plumb the brake lines & hoses to eliminate the ABS module but you will also have to remove the electronics box from the ABS module & make that waterproof then plug that back into the bike wiring harness. THEN also find a way to mask the dash warning light from shining (it isn't a removable bulb & it's signal gets to the dash module over the CanBus system )

Thanks very much mate. It certainly looks like a bypass at the present until I can source the parts. Thanks again.

FWIW, a German company that can rebuild the servo module: https://rhelectronics.de/produkt/type-am1/

I have no personal experience with the company, just saved the site in case I might need it some day.

They also offer a bypass kit to eliminate the ABS while keeping lights and speedo functions. Only slightly cheaper than an ABS rebuild, though.

Thanks.

Make sure to check any second hand module or any rebuilder to make sure that they can handle your model/serial number bike. When I was looking for replacement for my '05, none of the Ebay modules were compatible and the two potential rebuilders indicated that they didn't have right parts for my particular module.

At the time I was looking, about $1,200 was the lowest cost replacement part from an outfit in Germany. Most US vendors were around $2,400.

I ended up doing ABSectomy.

Sounds very daunting on the whole, but taken one part of the puzzle at a time, it is not that hard.

Ended up costing me nothing as I had an extra stainless brake hose from another project which was just right for the rear brake.

Dave

Yes mate I did the same. The abs lump has been removed and brake lines bypassed. The warning lights have been covered up to so back to a non abs bike. I have started dismantling the abs unit to see if the fault is with either the motors or the pressure sensors. Will keep you posted. Cheers

This post over at BMWMOA.org says Module Masters is now rebuilding iABS units, though their website has not yet been updated.

Thanks Larry for the info and link. I think that with so much time having passed, that I'd kind of given up hope that Module Masters was still working on this. The price is certainly attractive compared to the alternatives!

From the link Larry provided:

Q: How much will the rebuild cost when it's available?

A: $750 It will also include our 5-year warranty.