Well I am stuck with a Populo Lift that has a defective controller (I Think) and can not find any one who can help me of find a replacement. It will work for awhile then suddenly stops providing assist usually when I am going uphill. After a bit it will start to work again. Also the speedometer stops working and does not change modes as it should.
I have the exact same problem. Here is what I understand. The KM 529 LCD unit has an auto shutoff in 10 min so since you are not showing any speed it thinks the bike is not moving and it shuts down. I took the rear hub apart and on the cover, where the sprocket gears are, there is a single magnet inside surface (see pic below) and that magnet spins by this speed sensor. in picture it’s the 3blue wires that goto the small black sensor and sends out a voltage out to the controller found INSIDE the battery HOLDER small section in the front of the holder then out to the KM529 LCD display. How I checked the voltage output, on the right most blue wire, I put my multimeter on that pin and the middle blue wire- Gand and taking a magnet and placing over the speed sensor and measure 3.72VDC so I knew the speed sensor is working. Next you need to trace the wire out of the hub to make sure that wires ohms out. Next take the female end, found at the bottom of the frame close to the gear assembly, and ohm each female pin to the controller.
There is a gray plug where the controller is annd I THINK NOT SURE if this is where to ohm too. Anyways in my situation I ordered a new compatible LCD display through eBay $27 Thinking this would fix my problem at first it did not. I still cannot see the speed, but it is very programmable and I was able to set up the shut off time to never shut off or you can choose up to 60 minutes so now I can ride the bike without the unit shutting down. Eventually I will troubleshoot some more and find out exactly why I’m not getting that speed read back.