FIRST ELIMINATION
Check the brake cutoffs
Many e-bike controllers disable motor power whenever a brake sensor is active. A stuck or damaged brake cutoff can therefore make the display work normally while completely disabling the motor.
Disconnect the brake cutoff connectors temporarily and test the motor again.
- Motor now runs: troubleshoot the brake sensor or wiring.
- No change: continue to the battery voltage test.
POWER SOURCE
Verify battery voltage
A display can sometimes power up even when the battery cannot supply enough voltage or current for the motor system.
Measure battery voltage with a multimeter at the battery output.
- Normal voltage: continue to the controller input test.
- Very low or unstable voltage: troubleshoot the battery or BMS first.
POWER DELIVERY
Check voltage at the controller
The battery may be healthy while the controller receives no power because of a connector, fuse, switch or wiring problem.
Measure voltage directly at the controller battery input.
- Battery voltage present: continue testing the controller.
- No voltage: trace the wiring between the battery and controller.
LOW-VOLTAGE SUPPLY (SENSOR POWER)
Check the controller 5V supply
Most controllers provide approximately 5V to low-voltage devices such as the throttle, PAS sensor and Hall sensors.
Measure the controller's 5V supply using a multimeter.
- About 5V present: continue testing the control signals.
- 0V: suspect controller power circuitry, wiring or a shorted accessory.
Common questions
Can the display work if the controller is bad?
Yes. A display can power up even when the controller has a fault preventing motor operation.
Does no motor movement mean the motor is bad?
No. Brake cutoffs, wiring, throttle/PAS signals and controller faults can all prevent a working motor from running.
Keep the diagnostic checklist on your bench.
Use the EbikeFixIt Quick Diagnostic Guide while you work through a fault.