Brake failure light

sagalout

Registered user
Joined
Jun 13, 2012
Messages
1,232
Reaction score
0
Location
Harrogate, England
I've had a search but most results are for the older servo assisted bikes. Mines a 2012 Twin Cam and just got the brake failure light on it today when starting up for a quick ride. The bike has been stood for a couple of weeks over Christmas, where I did give the bike a good going over with ACF50.

Could it be that the ACF50 has got somewhere it shouldn't have? I've tried cleaning the front ABS sensor but can't see where the back on is?

Or do these bikes throw a warning when the pads get very low like cars do? Inspecting it today whilst charging the FD oil and the rear pads are very low (just ordered some new ones)

Thanks in advance!
 
ACF50 is non conductive so its not that

http://www.ridearound.net/maintenance/bmw-r1200gs-brake-warning/

Switch the bike off.
Flick the brake levers (front and rear) several times.
Switch the bike on.
If servos still do not work:
Switch bike off.
Whilst pushing front lever out & holding rear lever up…
Switch bike on.
If servos still do not work:
Switch bike off.
Check the rear brake light switch by the back level, ensure there isn’t any grit in it.
Switch bike on.
The reason for doing these checks is to ensure the bike doesn’t think the brakes are engaged when the bike is being switched on. As indicated in the rider’s manual:
 
I've had a search but most results are for the older servo assisted bikes. Mines a 2012 Twin Cam and just got the brake failure light on it today when starting up for a quick ride. The bike has been stood for a couple of weeks over Christmas, where I did give the bike a good going over with ACF50.

Could it be that the ACF50 has got somewhere it shouldn't have? I've tried cleaning the front ABS sensor but can't see where the back on is?

Or do these bikes throw a warning when the pads get very low like cars do? Inspecting it today whilst charging the FD oil and the rear pads are very low (just ordered some new ones)

Thanks in advance!

No, the pads do not throw up a fault light when worn.

The rear sensor is on the end of the black cable running along the top of the swing arm to the rear disc area and is accessed by removing the rear wheel and working through the disc.
There really is a boat load of info. on the forum on this subject and rather than wait around here for the replies to come in (which they will) i recommend you do searches and read up on all the threads.
If you fail to turn them up just report back here :thumb2
 
ACF 50 insulating the lever microswitch contacts? But you have to be slathering it on.
Check rear speedo sensor cable connector by rear shock top mount.


Sent from my iPhone using Tapatalk Pro
 
ACF 50 insulating the lever microswitch contacts? But you have to be slathering it on.
Check rear speedo sensor cable connector by rear shock top mount.


Sent from my iPhone using Tapatalk Pro

On a TC there are no micro switches on the levers. They are pressure switches in the abs unit.
 
On a TC there are no micro switches on the levers. They are pressure switches in the abs unit.

Unlikely as it ever was, it won't be that then. ;)

The final drive speedo sensors are amazingly unreliable. Start there and see what you find. I don't know of the GS 911 can diagnose a faulty sensor against a broken wire in the circuit.
 
Thanks for the responses. Would there be any other symptoms if it was the final drive speed sensor? Would the speedo work?
 
Thanks for the responses. Would there be any other symptoms if it was the final drive speed sensor? Would the speedo work?

The speedo would eventually fail but may not immediately. It happened to me last summer on my 2013 TC TB GSA and I had to get a new sensor. I had taken the wheel off and the sensor out and gave it a good clean but to no avail.
 
Thanks for the responses. Would there be any other symptoms if it was the final drive speed sensor? Would the speedo work?

If the speedo doesn't work for a couple of miles then springs into life then the rear ABS sensor has a fault as the
electronics have switched to using the front sensor for it's speed calculation data.
The sensor can have a partial failure where it sends corrupted data and in this case the symptom is as above.
If the sensor has failed completely and sending nothing then it will use the front sensor immediately.
A way of testing this is to raise the front wheel and with the ignition on spin it. If the speedo works then the rear
sensor has become disconnected or failed completely.
 
I’ll have to try that. Mine at the moment throws up the brake warning immediately then after (at least) 2 miles the speedo kicks in. I will disconnect the sensor and see if that changes the behaviour. It’s done exactly what the previous sensor did.

Do you think a cable fault could cause a partial failure?
 
If the cable is faulty but not completely broken it's a possibility.
If there is a signal being sent but is not coherent the controller will "listen" for a while then give up
and switch to the front sensor so a partial connection could possibly do that.
If you disconnect the plug under the seat you will find the speedo will work if you spin the front wheel with the ignition on.
 
I'll disconnect the rear sensor tonight and see what happens. If it does kick straight in, it will be odd that both rear sensors went down with what looks like a partial connection. I might splice a new wire into the old sensor and see if that sorts it. Pigs might fly but that might be all it needs.
 
Just to update this in case it helps others, it was the rear wheel speed sensor.

It had the symptom of the speedo not working for a few miles then kicking in, presumably from the front sensor. Cost was £110 from dealer, who couldn’t find the fault from diagnostics and wanted to spend an hours labour investigating. I told him to just replace it.
 


Back
Top Bottom