Speed sensor malfunction

[damdegraff]

Has anyone experienced issues with Trek Rail magnet/speed sensor? I am in the U.S. and when I start to reach speeds around 16 MPH I can see the speedometer get very iinconsistent and flicker between speeds of 16 to 20+ MPH, and consequently cut off the power assist because it thinks I am going 20MPH, when I am clearly not.

The shop said the magnet picks up metal from the street/dirt that affects the sensor, but I've tried cleaning both the magnet and the sensor to no avail.

Any help would be appreciated!
-Adam

 

[Stihldog]

The magnetic sensor was an issue on my rail. I believe the sensor wire goes to the motor which is a two wire water proof connection. It’s a fairly easy to access the wires once the skid plate is removed.

 

[DecoyD]

Didny

The magnetic sensor was an issue on my rail. I believe the sensor wire goes to the motor which is a two wire water proof connection. It’s a fairly easy to access the wires once the skid plate is removed.

What was the fix? Did you fix it by changing the sensor wire and sensor? Error513?

 

[Stihldog]

Didny

What was the fix? Did you fix it by changing the sensor wire and sensor? Error513?

I only pushed the two-wire connection to the motor. Dropped the skid-plate of course. The connection may have come loose from the vibration. I would check that first. I hope it’s not your sensor. Same problem found on my son-in-laws Rail 7.

 

[Yoak]

I had the same problem on my 9.8. Tried everything and read forums, upgraded software etc. Then I heard about the magnet issue. I tried cleaning my magnet, but the problem came back. Then I tried a friend's rear tyre from his 9.8 and everything worked flawlessly.
That meant it had to be the magnet.
I then unscrewed the magnet from the diskbreak and wiped it down properly and made sure I got rid of all the metal shavings from the breaks.
After that. I never had a problem with my wrong speed reading after that.
Make sure it's wiped down, as it's difficult to get rid of all the metal shavings. Good luck

 

[Yoak]

I jinxed myself?
For the first time this morning I got 503 error code. (Speed sensor). I just changed break disk and pads on the rear wheel so I thought I just needed to clean the magnet. I tried a few times. I managed to reset, but got the 503 back 2 times. Managed to ride home without error popping up again, but I could see my speed readings were all over the place. ?

 

[Stihldog]

Update; Son-in-laws Rail 7 started the 504 error again. The behaviour was; assist cutout, erratic speed displays and error 504 display on the purion. He booked a scheduled service and reset this week with the LBS. He may upgrade to the Kiox at that time. I found a small crack in the skid plate too. Ordered another one of those.
My issue was similar but was triggered from bumps or jumps which indicated a loose connection. I believe the speed sensor wire/plug had shaken loose at the motor. Easy fix.
I’m not sure what the 503 error is?
It would be nice if we could do a reset ourselves, thru an app, so we didn’t need a LBS appointment.

 

[Yoak]

The 503 has to do with the magnet and speed sensor.
I think I just made a mistake when I fitted the new rotor.

 

[Yoak]

Just quick update.
I managed to put on of the 3 washers that came with the new breaks behind the magnet. That “built” the magnet 1mm closer to the sensor and that was enough to get wrong readings. Removed the washer and no error codes since

 

[Esef]

Im opening this up again. On my Rail9 I swapped brakes and rotor for HopeTech. Since the aluminium part of the HopeTech rotor is thick my Bosch magnet is closer to the sensor and speed shown on the KIOX is jumping between 20-30kmph while Im pedaling 15kmph according to apple watch. It keeps cutting out the power so much and so often (every second) that it manage to unscrew sprocket security ring on the engine.

Question now is: Do I have poorly connected sensor in the engine as I replaced brake hose and disconnected the engine for the job? Or the sensor is indeed too close to the magnet since the Hope rotor is thick?

Is there someone else with this type of problem?
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