Strange rear speed sensor fault...

[G5RJO]

Bit of a saga...

Final drive filled up with water. Speed sensor was fine though.

Flushed it all out, rebuilt it. Speedo intermittent and red brake failure light. Checked the rear sensor it was not seated properly. Reseated it. Speedo works but brake still the same.

Out omes my GS911. Reports fault on speed sensor, it cleared as no longer present but move off and fault returns.

Sensor is clean, very clean, no filings etc etc.

Had final drive rebuilt, no rust on crown wheel etc so all good.

Speedo works fine. Brake fault remains and GS911 now can't clear the sensor fault.

Question is, how can it be faulty if the speedo works fine?

What else can it be?

Struggling

Roger

 

[B4ndit]

When my rear ABS sensor failed (I take it thats what your on about) the speedo wasn't affected. Although it lost the self cancelling function.

 

[GSaddict]

Same here

Coming back from borders bash last weekend, yellow triangle appears and brake failure light comes on.
Read through threads and booked the bike in, speedo failed to work, then a few miles down the road started working.
Any way changed final drive oil ( it was white ) cleaned the sensor connected the 911
And it only showed no abs signal detected.
Put it all back together' test rode, no speedo? Ordered a new sensor rode back, no speedo then a few miles it worked and odometer works but brake failure light still on and flashing abs on dash
Church Stretton m/c will contact BMW for further info and will try a new sensor.
Any one, any ideas

 

[Pukmeister]

I suspect the sensor has several outputs rather than one, eg a wire for speed, a wire for ABS plus a ground. Haven't got a wiring diagram to confirm this, just a hunch.

Either way, you need to fit someone else's sensor or a new one just to prove where the fault lies (or doesn't).

 

[GSaddict]

I suspect the sensor has several outputs rather than one, eg a wire for speed, a wire for ABS plus a ground. Haven't got a wiring diagram to confirm this, just a hunch.

Either way, you need to fit someone else's sensor or a new one just to prove where the fault lies (or doesn't).

Thanks, I will try that and post the results.

 

[G5RJO]

Sorted...

Ordered a replacement speed sensor, fitted it and away it went.

Red brake failure fault cleared itself, indicator self cancelling returned, speedo is fine and strangely the ESA preload has returned as that failed to work at the same time.

I reckon that the bike links all these things together somehow and, when the rear speed sensor fails then it picks up speedo signals from the front one. Hence the loss then return of the speedo.

All very strange bit sorted. Under £20 from Motorworks as opposed to £70+ from the stealers.

Roger O.

 

[GSaddict]

Ordered a replacement speed sensor, fitted it and away it went.

Red brake failure fault cleared itself, indicator self cancelling returned, speedo is fine and strangely the ESA preload has returned as that failed to work at the same time.

I reckon that the bike links all these things together somehow and, when the rear speed sensor fails then it picks up speedo signals from the front one. Hence the loss then return of the speedo.

All very strange bit sorted. Under £20 from Motorworks as opposed to £70+ from the stealers.

Roger O.

Thanks Roger, for that.

I am in the process of replacing the sensor, haven't thought about motoworks, will give them a go.

Cheers
D

 

[GSaddict]

Replaced speed sensor, all faults cleared

Thanks all, for the input.