Updated April 2026
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You changed a flat tire or had a shop replace your rear tube, and now pedal assist doesn't work. This is a very common issue with a simple fix.
When removing the rear wheel, the torque sensor cable or the motor wire can get disconnected, pinched, or damaged. Here's how to fix it.
The small green connector at the rear dropout may have been knocked loose during wheel removal. Unplug it and firmly replug it — you should feel a click.
When reinstalling the rear wheel, the torque sensor tab must sit correctly in the dropout slot. If the wheel was reinstalled without properly seating the torque sensor in its groove, it won't read your pedaling force.
Remove the rear wheel, verify the torque sensor tab is aligned with the dropout slot, and reinstall.
The larger connector (with thick wires) connects the motor to the controller. Ensure it's fully seated — it may have been pulled apart during wheel removal.
Unplug the torque sensor and try throttle only. If the throttle works fine, the issue is definitely with the torque sensor connection or cable — replug and retest.
If you replaced the tube yourself, check that you didn't pinch the torque sensor extension cable between the axle nut and the dropout. This is the most common cause when a home repair leads to pedal assist failure.
Tip for bike shops: If you take your Surface 604 to a local bike shop for a flat repair, let them know about the torque sensor connector at the rear dropout. Most shop mechanics are unfamiliar with eBike torque sensors and may not reconnect it after removing the wheel.
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