If the throttle drives the bike but pedalling does nothing, your battery, controller, motor and main wiring are all proven good. The fault sits in the pedal-assist chain — and roughly four out of five times it costs nothing to fix.
Work through these in order. Do not buy a sensor until you reach step 5.
Check the assist level is not on zero This is the single most common cause. It happens most often after a battery has been run flat — the display resets to level 0 and pedalling does nothing. Press UP or + and set it to 1–3.
Power cycle properly Switch off, remove the battery, wait 15 seconds, refit it. This clears a latched controller state that a normal off-on does not.
Check both brake levers return fully Nearly every e-bike has a cutoff switch in the brake levers that silences the motor. A lever resting a couple of millimetres in will keep the motor cut with no warning light. Squeeze and release both.
Check the cadence sensor plug and magnet gap The connector near the bottom bracket is easily knocked loose when removing the battery. Reseat it. Then check the magnet disc: it should sit 1–3 mm from the sensor head, run true without wobble, and be clean of grease and grit.
Only now: replace the sensor If all four checks pass and there is still no assist, the sensor itself has failed. Most use a universal 3-pin waterproof plug.
Why the assist level resets itself
When a lithium pack is discharged deeply, the controller can lose its stored settings on the next power-up. Assist returns to 0, and because the throttle is a separate input, throttle still works perfectly. That combination — throttle fine, pedalling dead, right after the battery went flat — is the signature of this fault, not of a broken sensor.
Cadence sensors and throttles If you have worked through all five steps, the replacement parts are here. Not sure what's wrong? Run the three-minute check first — most pedal-assist faults need no new part at all.RideRow sells replacement parts and provides installation information. We do not perform repairs. Installation is carried out by you or a technician you choose.