Power assist keeps cutting out on Giant Trance (Yamaha motor)

[Andy B]

I've just bought a Giant Trance X Advanced 2022 with a Yamaha engine. On my first trip I found the power assist kept cutting out at very inopportune moments (e.g. when climbing). This happened about 10-12 times during a 3 hour ride. When this happened a single red LED appeared on the display. The only way to get power back was to turn off the system and restart it again.
Can anyone offer any reasons for this please and how to resolve it?
P.S. It wasn't a hot day and the battery wasn't overheating.

 

[major masingil]

I don't own that type of bike, sorry. I would go on Giant's website and download the user manual for your model. You should be able to find out what the led light is intended to represent. That's probably the safest place to start.

The next time it happens check the temp of the motor. Pay attention to what gear you are in and how much leg power you are using on the hill vs how much of the work you are asking from the motor. Those are torque sensing motors, correct? If it's not a technical issue with the bike itself, it could be a battery low voltage cut-off or you could have been in too high of a gear for the hill and pedaling too slowly. Come back and let us know the deets! Good luck!

 

[woodyhill]

I bought a 2022 Trance e-3 and had same problem, but never got the red light. The motor would always start again but frustating to be always stopping & starting. Took it back to the shop and the guy adjusted the battery clamp and went well for about a year. Whenever the battery starts cutting out, I just stop trailside, remove battery & reinsert with the bike upright, and tighten it all up and then goes well again. Can't explain the fix but maybe the contacts work loose. Always carry the Torx T25 now.

 

[Andy B]

I don't own that type of bike, sorry. I would go on Giant's website and download the user manual for your model. You should be able to find out what the led light is intended to represent. That's probably the safest place to start.

The next time it happens check the temp of the motor. Pay attention to what gear you are in and how much leg power you are using on the hill vs how much of the work you are asking from the motor. Those are torque sensing motors, correct? If it's not a technical issue with the bike itself, it could be a battery low voltage cut-off or you could have been in too high of a gear for the hill and pedaling too slowly. Come back and let us know the deets! Good luck!

Update-
There is no pattern or logic to the number of times or in what situation the motor keeps cutting out. I've tried riding in lower gears than normal and I've tried leaving it in the auto position, but still get the same result: It cuts out without any explanation and at irregular times. I've had to abandon some rides after 30min of stop/start issues
In the end I took it to a Giant dealer who took the battery out and updated the software. However this did not work. I've left it with him scratching his head as he'd never seen thus before. Even the head technician at Giants UK HQ couldn't offer any suggestions!
It's now going to be a process of installing new parts until something (hopefully!) fixes it! Not looking forward to the bill!

 

[Andy B]

I bought a 2022 Trance e-3 and had same problem, but never got the red light. The motor would always start again but frustating to be always stopping & starting. Took it back to the shop and the guy adjusted the battery clamp and went well for about a year. Whenever the battery starts cutting out, I just stop trailside, remove battery & reinsert with the bike upright, and tighten it all up and then goes well again. Can't explain the fix but maybe the contacts work loose. Always carry the Torx T25 now.

My problem has persisted despite me adapting my riding style to the point that I had to take it to the closest Giant dealer. He took the battery out and updated the software but this didn't cure it. He was then stumped so rang Giant's UK HQ to see if they could help. Sadly nothing offered as he too was flummoxed by the irregularity of when it cuts out.
Now it's just a case of replacing parts until we get the dodgy one removed!
Thanks fir for your suggestions anyway

 

[Motley]

Did the crank sensor get wet ride through a puddle or in the rain for a few minutes since they’re so sandwich together they can hold water for a little bit but they also can be a little intermittent and picky. They’re only a few dollars to buy. I suggest replacing it and look at the wires and the plug and how it goes on your crank and buy one exactly like it. Some of these Bike sites don’t offer parts and when they do, they can be expensive when you can just match up and buy the parts.

 

[Annieolnie]

The EMTB forums have this as a recurring problem. The one simple thing that crops up is the magnet sensor on the back wheel being out of place or misaligned and that does bring up a red light on the display. People do have a number of issues but that is an easy one to check.

 

[maniacalmotor]

I have a similar issue of motor drop out / red flashing light when going up steep hills on 22 Trance X Advanced Pro 0. Dealer diagnosed faulty torque sensor through ‘plug in’ diagnostics (vs wireless diagnostics). Fix is a replacement motor. 2-3 month wait in Australia at the moment from Yamaha.apparently. Hopefully the new motor solves the issue.