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Display on but no motor assist? Here's the order to check
When the display works but the motor does nothing, the system has decided not to give power: a brake sensor, a speed sensor, a wrong mode, or a loose motor connector. Most of these are five-minute fixes once you know where to look.
Quick checks, in order
- Check the assist level on the display. Eco/Off or level 0 gives no help at all, and it is easy to press the wrong button.
- Squeeze and release each brake lever a few times and look for a brake symbol on the display. A stuck brake sensor cuts the motor completely.
- Turn the bike upside down or lift the rear wheel and spin it. On the display the speed should read. No speed reading means the speed sensor or its magnet is out of place, and most systems refuse assist without a speed signal.
- Pedal with real force from a stop. Torque-sensing systems need actual pedal pressure; spinning the cranks with no load gives almost nothing.
- Switch the system off, remove the battery, wait 30 seconds, refit and restart. Many temporary lock-outs clear this way.
- Check the walk-assist function. If walk assist moves the wheel, the motor and its wiring are fine and the fault is a sensor or a setting.
- Look for an error code, wrench, or exclamation symbol on the display; even a small icon usually explains the no-assist condition.
Likely causes
Speed sensor not reading (magnet moved, sensor loose, or dirty)
How to tell: Speed shows 0 while riding. Bosch shows 503, Shimano W011, Bafang 21, Yamaha 11. Magnet on the spoke has rotated away from the sensor, or the sensor is caked in mud.
Fix: Align the spoke magnet with the sensor mark, 5-10 mm gap. Clean the sensor. On Bosch rim-magnet systems check the magnet on the disc rotor is present and the sensor cable is plugged in.
How to tell: Speed shows 0 while riding. Bosch shows 503, Shimano W011, Bafang 21, Yamaha 11. Magnet on the spoke has rotated away from the sensor, or the sensor is caked in mud.
Fix: Align the spoke magnet with the sensor mark, 5-10 mm gap. Clean the sensor. On Bosch rim-magnet systems check the magnet on the disc rotor is present and the sensor cable is plugged in.
Brake sensor stuck or misadjusted
How to tell: Brake icon stays on the display, or assist cuts when you touch the lever and never comes back. Common after a lever swap or a crash.
Fix: Adjust the sensor magnet on the lever, or unplug the brake sensor connector to confirm (assist returns = sensor fault). See the brake sensor guide.
How to tell: Brake icon stays on the display, or assist cuts when you touch the lever and never comes back. Common after a lever swap or a crash.
Fix: Adjust the sensor magnet on the lever, or unplug the brake sensor connector to confirm (assist returns = sensor fault). See the brake sensor guide.
Torque or cadence sensor not seeing pedal input
How to tell: Display and speed fine, motor gives nothing however hard you pedal, walk assist works.
Fix: Cadence systems: check the sensor disc at the crank is intact and the sensor is 1-2 mm from it. Torque systems: switch off, take your feet off the pedals, switch on so the sensor zeroes. A failed torque sensor needs the dealer.
How to tell: Display and speed fine, motor gives nothing however hard you pedal, walk assist works.
Fix: Cadence systems: check the sensor disc at the crank is intact and the sensor is 1-2 mm from it. Torque systems: switch off, take your feet off the pedals, switch on so the sensor zeroes. A failed torque sensor needs the dealer.
Motor connector loose or corroded
How to tell: Assist cuts out over bumps, grinding or shuddering before it stopped, motor hums but does not turn.
Fix: Hub drives: unplug the 9-pin motor connector, check for green or burnt pins, plug in with the arrows aligned. Mid drives: the motor cable is internal, so this is a shop job.
How to tell: Assist cuts out over bumps, grinding or shuddering before it stopped, motor hums but does not turn.
Fix: Hub drives: unplug the 9-pin motor connector, check for green or burnt pins, plug in with the arrows aligned. Mid drives: the motor cable is internal, so this is a shop job.
System in a safety lock-out (temperature, over-current, or a code that cleared itself)
How to tell: No assist after a long climb, a hot day, or a stall. Comes back after 10-20 minutes.
Fix: Let the motor cool with the system off. If it repeats on every ride the motor or controller is on its way out.
How to tell: No assist after a long climb, a hot day, or a stall. Comes back after 10-20 minutes.
Fix: Let the motor cool with the system off. If it repeats on every ride the motor or controller is on its way out.
Controller failed (hub-drive systems)
How to tell: Display on, no assist, no walk assist, no error. Sometimes a burnt smell from the controller box.
Fix: Replace the controller. Match voltage, current rating, and display protocol.
How to tell: Display on, no assist, no walk assist, no error. Sometimes a burnt smell from the controller box.
Fix: Replace the controller. Match voltage, current rating, and display protocol.
Bike locked or in a service/transport mode
How to tell: Bosch Smart System with eBike Lock shows a padlock; some fleet bikes have an app lock. Display works but assist refuses.
Fix: Unlock with the phone or the paired display. If the bike is second-hand, the previous owner's app may still hold the lock.
How to tell: Bosch Smart System with eBike Lock shows a padlock; some fleet bikes have an app lock. Display works but assist refuses.
Fix: Unlock with the phone or the paired display. If the bike is second-hand, the previous owner's app may still hold the lock.
By drive system
- Bosch: Bosch will not assist without a speed signal; check the speed sensor and magnet first (code 503 if it is missing). eBike Lock in the Flow app blocks assist until unlocked. If walk assist works but pedalling does not, the torque sensor in the drive unit is the suspect and needs DiagnosticTool.
- Shimano STEPS: W011 (no speed detected) is the classic no-assist cause: check the speed sensor magnet on the disc rotor and the SM-DUE sensor. W013 means the torque sensor did not zero; restart with no feet on the pedals. Brake sensors on Shimano are only fitted to some bikes; if fitted, check them.
- Bafang: Bafang codes 21 (speed sensor), 25 (torque signal), and 08 (hall sensor) all show as no assist. BBS mid-drives have a speed sensor on the chainstay; the magnet on the spoke must pass within 10 mm. Brake cut-off sensors on Bafang are frequently the cause; unplug them one at a time to test.
- Yamaha PW: Error 11 (speed sensor) is the first thing to check. Yamaha PW-series torque sensors are reliable; if walk assist works but pedal assist does not, restart with no load on the pedals so the sensor calibrates. Yamaha stops assisting if the rear wheel speed sensor is more than about 8 mm from the magnet.
- Generic: Most cheap hub systems are cadence-based: a magnet ring at the crank and a sensor. If the ring is cracked or the sensor is knocked away there is no assist. Then check the brake sensors (unplug to test), then the 9-pin motor plug, then the controller. Throttle working while pedal assist does not points at the cadence sensor.
When to stop: Go to a shop if the motor hums, grinds, or smells hot, if a mid-drive gives no assist after the speed sensor and brake sensors check out, or if you would need to open the motor or drive unit.
Related error codes
Bosch 503Bosch 504Bosch 510Shimano STEPS W011Shimano STEPS W013Shimano STEPS E025Bafang 21Bafang 25Bafang 08
Still stuck? Take a photo of the display and show it to a local e-bike workshop. Bring the bike's system name (e.g. Bosch Performance Line CX) and the exact code; that saves diagnostic time and money.
Frequently asked
Walk assist works but pedalling gives nothing. What does that tell me?
The motor, battery, and controller are fine. The system is not seeing your pedalling: torque or cadence sensor, or a brake sensor telling it to stop. Check the brake sensors first, they are cheaper.
Assist only works above a certain speed or only below it.
That is a speed sensor giving a bad reading, or the speed limit set wrong. Check the magnet gap and the wheel-size setting on the display.
Could the battery be too low to run the motor even though the display works?
Yes. Most systems shut off assist a little before the display goes dark, so the last bar of battery is not really usable. Charge it and try again before chasing anything else.