Brake failure and intermittent speedo

Hi,
I've got an annoying problem with my bike.

This has happened 4 times now - each time I hadn't ridden the bike for 2 or maybe 3 months, then on the first first, the brake failure red light will turn on solid, the ABS symbol will flash on the screen, and the speedometer won't work. Obviously no ABS functions.
However, after travelling 5-7 miles, sometimes quicker with higher speeds, the speed will suddenly start working, though the brake failure light remains on. However, if I turn the ignition off, the speedo doesn't work for a few miles again.

The first time it happened, I was on a tour, but during the course of the tour the problem went away by itself.
The second time that it happened I found a loose positive terminal, the problem went away after that.
The third time, this time last year, I felt the ABS pumping (despite riding at low speed in grippy conditions, no way the ABS should have been kicking in). That's when the error started. I took the bike in for its annual service, and the garage cleaned the rear wheel speed sensor, which made the problem go away.

Cue riding the bike this week - I last rode it in January - and same issues. Today I cleaned the rear wheel speed sensor. I didn't see any noticeable amount of shavings or filings on it. The oil did look a little bit grey however. Unfortunately that hasn't fixed it - still the same issue, a few miles into the ride the speedo comes back, but doesn't work if I recycle the ignition.

The bike is a 2011 GS Adventure, which 35,000 miles on the clock. Brake fluids front and rear are fine. The brake lights work as they should do (They are the OEM LED bulbs). The battery connections are good, I've checked those. The battery is also ok. Unfortunately I don't have a GS-911 tool.

I'm planning to change the final drive oil, as there was one person with similar symptoms to mine that seemed to fix this, but I'm not so convinced that it will make any difference on a sealed sensor unit.
After that the only other thing I can think of is to replace the speed sensor. Has anybody got any other ideas of what might cause it (and why the speedo seems to wake up after a few miles?)

Thanks in advance,
Ventzi

Take the rear speed sensor out and clean the gunk of the end of it. The sensor is magnetic and attracts metal in the oil from the FD which stops it working properly.

Thank you.
I have done, but it didn’t actually have any gunk on it really, so just ended up cleaning the oil from it

You have one or possibly four faults

Fault one

Your battery is dying, low voltage can play havoc with the bikes sparkerybits

Fault two

ABS/ Servo unit is in its death throes - you can replace circa £1200 from the mothership

Or alternativly perform a servoectomy for about £50

Fault 3

Rear ABS sensor is failing -the rear fails hence no speedo - after 5 miles of no readings being detected by the ZFE / Kombi it switches to the

speed impulses from the front ABS sensor


Fault 4

The rear cardon drive is dying and the reluctor ring inside the unit is clogged with oily shite & debris

Solutions

Check battery voltage - charge replace if required

Repair / replace ABS Servo unt

Replace rear ABS sensor

Drain & refil rear cardon drive with fresh oil

Thank you so much, that all sounds about on the money.

The battery I’ve already tested - and short of just changing it for a brand new one, I’m pretty happy that it’s ok.

The other stuff though - I’m going to start with the oil change, then the sensor change, then if it’s still an issue - I’ll have to cross that bridge when I get there!

Thank you again for your reply. I’ll remember to reply once I work out what caused it for any others that search and get the same problem

I have a repaired but not tested rear sensor, cable was chafed by disc after it came out of the clip on the final drive housing. You are welcome to borrow it to see if it fixes issue and if it does I will know I have a serviceable spare. They are not cheap, even used from motorworks are £75+. PM me if you want to give it a go.
I lost speedo, got brake failure and ABS warning lights.

Al.

Another thing to check is the wiring connector for the rear speed sensor, I know of two bikes where the connector came loose intermittently and caused similar issues.

If I remember rightly the connector is alongside the outer frame rail on the offside under the front seat

Thanks Al,
I’ve sent you a private message.

Neil, I’ve checked the rear speed sensor, and reseated that connection. However haven’t checked the front, as that looks like I need to take the tank off to get to, however sounds like it’s more likely to be the rear sensor as the speedo isn’t working.
Cheers

I’m struggling to find any oil marked as saf-xo but this stuff in the 75w-90 is GL5 rated, does this look like the right stuff?

https://www.castrol.com/en_gb/united-kingdom/products/cars/axle-universal-fluids.html

Santa-2512 said:

Fault two

ABS/ Servo unit is in its death throes - you can replace circa £1200 from the mothership

Or alternativly perform a servoectomy for about £50

Click to expand...

It's a 2011 bike. No servo.

tuonov said:

I’m struggling to find any oil marked as saf-xo but this stuff in the 75w-90 is GL5 rated, does this look like the right stuff?

https://www.castrol.com/en_gb/united-kingdom/products/cars/axle-universal-fluids.html

Click to expand...

I use Castrol Syntrax long life 75/90 for final drive and gearbox in my bike. I think it's the replacement for saf-xo.

Steptoe said:

It's a 2011 bike. No servo.

Click to expand...

oops teach me to speed read lol

no servo it is then

A slight update, I've changed the final drive oil, but unfortunately still no better.

I'm going to try changing the rear speed sensor, hopefully that will cure it. There is a worry that it might be the ABS controller. Hopefully not though!

I had the same issue, a new rear abs/speedo sensor fixed it.

Fixed - new rear wheel speed sensor has sorted it (probably - as cleaning it sorted it last year! Hopefully sorted for good now though)

Don’t you just love a happy ending��

Definitely. I made a point of updating, in my search for this problem, found plenty of threads online but not many had the solution, and I’m guilty of doing the same myself. At least this is sorted (hopefully!)

tuonov said:

Fixed - new rear wheel speed sensor has sorted it (probably - as cleaning it sorted it last year! Hopefully sorted for good now though)

Click to expand...

I have the exact symptom as yours... the usual error with delayed speedo reading after certain distance...Mine is a 2010 DOHC. I am into my 3rd rear speed sensor and the 4th one is on backorder. Everytime this error pops up, i did not change the rear sensor immediately(sometimes i delayed for a year before changing out)

1st failure was back in 2012 while i was on a trip.
2nd failure happened when i tore down my FD to change out the oil seal in 2014
3rd failure happened in 2016, just months after i changed out the sensor that were long overdue from the 2nd failure

I was particularly pissed with the 3rd failure. The failure happened after i did an emergency brake at the traffic lights. The error came back immediately and was hanging around happily with me for the past 2 years.

I changed all the sensor myself and everytime i make an effort to measure the resistance of the new and old. The readings are very close which puzzled me as i was expecting big differences in readings. However all new sensors work as it should on installation.

I also have water ingress problem with my FD but i do not have any metal shavings on the sensors.

I will likely try the ABS motor remedy next since i read many of us here had good results from this.

Brake failure warning and no speedo

Happened on my 2012 gs, read all the horror stories of a £1500+ cost to fix, gave it to my local dealer who pluged in the diagnostic thingy that that apparently cost a fortune to buy.

Rear wheel sensor was found to be faulty, replaced and I was on my way fault free, all for the measly sum of £80 happy days.