Speed Sensor - Which ones bust, deduction ?

[Wreford Miles]

So here’s the questions that’s baffling me...

A few years back my rear wheel sensor went, deduction with the help of the wise ones on here pointed to the rear sensor because:
As well as the brake warning light the speedo stopped working but would start again after a few miles - I understand this is because if it can’t get a signal from the back it will after a period (a few miles) pick up the speed from the front wheel sensor.

A year back my bike started to occasionally stutter like the traction control was operating and shortly after the brake warning light came on - The speedo kept working.

So I’m thinking front wheel sensor - I found if I wiggled the cable from the front sensor I could get the brake fail light to go out but when riding I’d get the occasional traction control stuttering. Eventually the brake warning light would come back on and no stuttering would follow.

My deduction had been the front sensor connection is flakey and my solution was don’t wiggle it to try and get a connection just leave it with the brake fail light and accept no ABS till I get around to fixing it - That means next service as I’m a clump and whilst replacing a rear sensor is within my capabilities a tank off front sensor change could lead to all kinds off self inflicted fuck ups.

Next service due I pop in to say it will need a front sensor and it’s plugged in for diagnostics which showed:

The front sensor did have a fault but none is showing now
The rear has a fault

So the plan was ignore my deduction as ‘ it’s quite possible that being a clump' my deduction is wrong and fit a new rear sensor first - This has not yet been done, so according to the diagnostic gizmo my bike has a rear sensor fault.

...However I’m riding out of London last night after a rather tasty pizza at Apollo in Stoke Newington (highly recommended) and I realise that the speedo does not have a period of not working when you start which is a sign (I thought) that the rear sensor was kaput. Making me think despite what the diagnostic thing said that it can’t be the rear sensor and must be the front because a wiggle use to fix things, or something else.

Any thoughts on next steps?

Thank you oh wise ones

Wreford

 

[Wreford Miles]

...just remembered that during the period when I had no brake warning light but the occasional traction control type stutter, the speedo would also flicker the speed showing suggesting the fault was affecting the Speedo’s pick up. The flickering would stop as soon as the brake fail light came on, which I took as meaning the flakey front wheel sensor connection, which was my fault deduction (not proven) had failed and it no longer interfered with the speed the speedo was picking up from the rear wheel.

 

[botus]

I'd be surprised if the speedo can work off the front at all,

I also have personal experience the TC can struggle but the ABS is perfectly happy

TC uses differences between front to rear wheel speed and data received is critical, whereas rather perversely, ABS seems quite happy with a partially failing rear sensor, had to disable TC as bike was unrideable, but at no point did ABS have an issue nor did I get any lights for the brakes.
Next point it the rears fail all the time
BMW's diagnostic can identify the front as faulty, but its actually the rear that's failed - which the tech's at this county's biggest motoradd dealership learnt fixing my bike under warranty

 

[UturnTony]

I'd be surprised if the speedo can work off the front at all,

I also have personal experience the TC can struggle but the ABS is perfectly happy

TC uses differences between front to rear wheel speed and data received is critical, whereas rather perversely, ABS seems quite happy with a partially failing rear sensor, had to disable TC as bike was unrideable, but at no point did ABS have an issue nor did I get any lights for the brakes.
Next point it the rears fail all the time
BMW's diagnostic can identify the front as faulty, but its actually the rear that's failed - which the tech's at this county's biggest motoradd dealership learnt fixing my bike under warranty

It can and does if the rear fails. It will, in the event of a rear sensor failure switch to getting the speed info from the front sensor.