Brake Fail Light and Wheel Sensor ?

Wreford Miles · May 21, 2017

Whilst in Dent a warning and Brake Failure light came on and bit of back brake confirmed no ABS was working...

On the way home I stopped to change the preload but it would not allow it, which made me think 'wheel sensor' and the bike does not know Ive stopped.

Also a quick scroll through the info while moving showed the 'oil' which is normally only seen while stopped.

Wheeled the bike out of the garage today and it allowed me to change the preload however a trip to the garage to fill up for the weeks duties showed the speedo not working for about two miles but then it started.

Now I've a 330BMW and that's had several wheel sensors replaced after it's told me I've no ABS or traction control or even that clever stuff that supposedly stops exiting a bend backwards, so with all this insight I'm guessing...

My brake failure is not due to some expensive ABS pump thingy but just the wheel sensor or something associated to it...

BTW I may have been over zealous with the jet wash around the brake calipers and the wheel sensor.

What's the wise verdict of the 'knowledgable' :thumb2

Cheers

Wreford

Bendy toy · May 21, 2017

Mine did similar things though I didn't notice the oil level symptoms. The oil level will display when the connector contacts are dirty. Disconnect, squirt in some contact cleaner (not WD 40) and reconnect. If that's not solved it, you can carefully clean the contacts with a diamond needle files and try again.

Check the speedo sensor connector by the rear shock top mount (same as above), but its likely you need a new speedo sensor in the back wheel.

Wreford Miles · May 21, 2017

Bendy toy said:
Check the speedo sensor connector by the rear shock top mount (same as above), but its likely you need a new speedo sensor in the back wheel.

I was assuming it was the sensor on the front wheel, I couldn't see one on the back but I did not look that hard

adventuredon · May 21, 2017

Wreford Miles said:
I was assuming it was the sensor on the front wheel, I couldn't see one on the back but I did not look that hard

look for the rear sensor from the back left of the bike, towards the final drive. You should be able to see the wire snaking along the final drive. Its a wheel off job to remove and clean if i remember correctly?

Pukmeister · May 22, 2017

I had the same issues, bike needed a new rear wheel speed sensor.

They arent cheap !

Fozzy · Jun 4, 2017

Hi All
My 2011 GSA started with this problem when 20 miles into a 1000 mile trip - the 'brake failure' light came on and stayed on plus every time I started off the speedo would not work for the first approx 3 miles. I continued my journey without ABS and visited this forum at the first opportunity to get some really useful info and came to the conclusion that the rear speed sensor was the problem. I read a post from 'mikeey' who concluded that emulsified oil in the rear hub was his issue. Now when I bought this 2011 GSA about 18 months ago I changed the oil in the rear hub (Motul Gear 300, 75/90 synthetic) and I noticed the old oil was rather grey. I've done about 5000 miles since then (mostly dry). I drained the oil again and this time it was really almost white - looked like double cream. So I flushed out the old oil and refilled - no more warning lights or speedo issues - thanks mikeey!
I suggest that anyone who has issues like this should first crack open the rear hub drain plug and check the colour of the oil - if its grey/white change it before you continue investigations or spend any more money.
Not sure where this water (if it is water) is coming from though. I should have saved some of the old oil to see if separated.

Wreford Miles · Jun 4, 2017

Interesting, mine does the 3 miles before the speedo works thing...

It's just been serviced and the diagnostics showed a faulty rear sensor ( now on order )

Although it was not due I did ask that the rear dig oil was changed, they did not mention that the oil that came out did not look healthy

UturnTony · Jun 4, 2017

Fozzy said:
Hi All
My 2011 GSA started with this problem when 20 miles into a 1000 mile trip - the 'brake failure' light came on and stayed on plus every time I started off the speedo would not work for the first approx 3 miles. I continued my journey without ABS and visited this forum at the first opportunity to get some really useful info and came to the conclusion that the rear speed sensor was the problem. I read a post from 'mikeey' who concluded that emulsified oil in the rear hub was his issue. Now when I bought this 2011 GSA about 18 months ago I changed the oil in the rear hub (Motul Gear 300, 75/90 synthetic) and I noticed the old oil was rather grey. I've done about 5000 miles since then (mostly dry). I drained the oil again and this time it was really almost white - looked like double cream. So I flushed out the old oil and refilled - no more warning lights or speedo issues - thanks mikeey!
I suggest that anyone who has issues like this should first crack open the rear hub drain plug and check the colour of the oil - if its grey/white change it before you continue investigations or spend any more money.
Not sure where this water (if it is water) is coming from though. I should have saved some of the old oil to see if separated.

If the rear sensor is giving a signal but it isn't understood by the ecu it will wait a while (in your case 3 miles) and then switch to using the front sensor
for a speed reading. If the rear sensor is completely duff and giving nothing out ie. as if disconnected, it will use the front sensor immediately ie. no waiting.

Wreford Miles · Jun 5, 2017

UturnTony said:
If the rear sensor is giving a signal but it isn't understood by the ecu it will wait a while (in your case 3 miles) and then switch to using the front sensor
for a speed reading. If the rear sensor is completely duff and giving nothing out ie. as if disconnected, it will use the front sensor immediately ie. no waiting.

Interesting, its all clever stuff nowadays...

What's the view of others on the condition of the diff oil being a possible cause?

UturnTony · Jun 5, 2017

Wreford Miles said:
Interesting, its all clever stuff nowadays...

What's the view of others on the condition of the diff oil being a possible cause?

I can only assume that if the oil contains an appreciable amount of metal particles these will tend to migrate to the ABS sensor pickup magnet and
possibly cause an incoherent signal for the ecu to read resulting in the error.
Cleaning the magnet and changing the oil would, in that case, rectify the problem.

Fozzy · Jun 6, 2017

UturnTony said:
I can only assume that if the oil contains an appreciable amount of metal particles these will tend to migrate to the ABS sensor pickup magnet and
possibly cause an incoherent signal for the ecu to read resulting in the error.
Cleaning the magnet and changing the oil would, in that case, rectify the problem.

Thanks for the explanation on the delay of the speedo working. I can add that there were no metal particles or any kind of grey sludge like you get in the drain plug visible on the sensor - I took it out before changing the oil. The oil had only been in there for about 18 months/5000 miles but was white in colour when it came out. I assume it was contaminated with water but you would think that if water could get in the you would see some evidence of oil getting out - but I don't. Also is the sensor actually magnetic?

Santa-2512 · Jun 6, 2017

Fozzy said:
Thanks for the explanation on the delay of the speedo working. I can add that there were no metal particles or any kind of grey sludge like you get in the drain plug visible on the sensor - I took it out before changing the oil. The oil had only been in there for about 18 months/5000 miles but was white in colour when it came out. I assume it was contaminated with water but you would think that if water could get in the you would see some evidence of oil getting out - but I don't. Also is the sensor actually magnetic?

The sensor is an induction coil, it creates a magnetic field when it energises.

The reluctor ring (looks like a circle with lots of oblong holes in it) passes through this field and causes a disruption of the magnetic field due to the holes

So your creating a pulse 1010101010101010101010 the pulse is sent to the ecu which does the clever bit .

If a wheel locks up the signal would be 10101111111 or 00000000 the ecu sees this and the abs valve opens releases the pressure to the caliper and the wheel

rotates 1010101010101 the abs unit shuts the valve and monitors

bear in mind this happens in fractions of a second ...

They are starting to use similar systems for engine timing on automatics...

Instead of a huge flywheel, a lighter unit with a reluctor ring on the outside is used.

The reluctor ring has different sized holes that tell the ecu TDC , ignition trigger etc.

Hope i wasnt trying to teach you to suck eggs

Mart

Bendy toy · Jun 7, 2017

UturnTony said:
I can only assume that if the oil contains an appreciable amount of metal particles these will tend to migrate to the ABS sensor pickup magnet and
possibly cause an incoherent signal for the ecu to read resulting in the error.
Cleaning the magnet and changing the oil would, in that case, rectify the problem.

If that's the case. you will be needing to send the final drive box to Mikey PDQ. Mine was sent when the main wheel bearing failed no signs of anything bad in the oil, but Mike said all internal bearings were shot.

Fozzy · Jun 8, 2017

Santa-2512 said:
The sensor is an induction coil, it creates a magnetic field when it energises.

The reluctor ring (looks like a circle with lots of oblong holes in it) passes through this field and causes a disruption of the magnetic field due to the holes

So your creating a pulse 1010101010101010101010 the pulse is sent to the ecu which does the clever bit .

If a wheel locks up the signal would be 10101111111 or 00000000 the ecu sees this and the abs valve opens releases the pressure to the caliper and the wheel

rotates 1010101010101 the abs unit shuts the valve and monitors

bear in mind this happens in fractions of a second ...

They are starting to use similar systems for engine timing on automatics...

Instead of a huge flywheel, a lighter unit with a reluctor ring on the outside is used.

The reluctor ring has different sized holes that tell the ecu TDC , ignition trigger etc.

Hope i wasnt trying to teach you to suck eggs

Mart

Not at all - good to get an explanation of this stuff. I don't think metal particles/wear is the problem - the drain plug contains a strong magnet and I only got a bit of grey paste out of it. It doesn't seem logical I know but I have convinced myself that water ingress caused the 'white' oil and the white oil affected the speed sensor. Maybe water is getting in around the drive shaft...I didn't notice anything last time I greased the UJ/drive shaft splines but I'll look more carefully next time.

Brake Fail Light and Wheel Sensor ?

Wreford Miles

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Bendy toy

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Wreford Miles

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adventuredon

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Pukmeister

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Fozzy

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Wreford Miles

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UturnTony

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Wreford Miles

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Fozzy

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Santa-2512

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Bendy toy

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