Shimano STEPS error W103: Sensor initialization warning at startup
The drive unit failed to initialise the torque or cadence sensor during the boot sequence. Assist is typically cut until the system completes a clean start, and walk assist is usually disabled as well. The display remains on but the bike will not respond to pedalling input until the warning clears.
| Drive system | Shimano STEPS (E5000, E6100, E7000, E8000, EP6, EP801) |
| Severity | Warning |
| Keep riding? | Ride with caution |
| Typical cost | Diagnostic at a Shimano dealer runs €30 to €60, a standalone torque sensor replacement €120 to €220 part plus €60 to €90 labour, and a full drive unit exchange with integrated sensor €400 to €700 fitted. |
Likely causes
- Pressure on the pedals when the system was switched on, blocking sensor calibration.
- Loose or oxidised connector at the bottom bracket torque sensor.
- Crank magnet ring dirty, bent, or out of alignment with the sensor.
- Stale firmware after a battery swap or recent dealer update.
- Water ingress into the drive unit bottom bracket area after heavy rain or pressure washing.
How to fix Shimano STEPS error W103
- Dismount and make sure both pedals are unloaded, with the cranks horizontal and free to rotate.
- Hold the power button for about 2 seconds until the display goes dark.
- Wait 15 seconds to allow the drive unit to fully discharge.
- Power the system back on without touching the pedals or rotating the cranks.
- Pedal gently once the assist icon appears to confirm normal operation.
- If W103 returns, lift the chainstay cover and check the torque sensor plug for corrosion or correct seating.
- Take the bike to an authorised Shimano dealer if the warning persists after two clean no-load restarts.
Warranty: A genuine torque sensor or harness failure inside the two-year Shimano warranty window is normally covered as a manufacturing defect, while crash damage, pressure-wash water ingress, and worn magnet rings are treated as wear and excluded.
Typical cost: Diagnostic at a Shimano dealer runs €30 to €60, a standalone torque sensor replacement €120 to €220 part plus €60 to €90 labour, and a full drive unit exchange with integrated sensor €400 to €700 fitted.
Frequently asked
Can I reset Shimano error W103?
Yes. Switch the system off, remove all load from the pedals, wait 15 seconds, then power on without touching the cranks. The warning clears if the torque sensor initialises correctly on the second attempt.
Is it safe to keep riding with W103?
The bike will roll without assist and walk mode is usually disabled, so you can ride home cautiously using your own effort. Stop at the first safe spot and try the no-load restart before continuing any distance.
Will Shimano cover W103 under warranty?
If the torque sensor or its harness fails inside the two-year warranty period it is treated as a component fault and replaced at no cost, provided there is no sign of impact damage, pressure-wash water ingress, or unauthorised modification.
Related Shimano STEPS codes
Manuals and video
Official source: si.shimano.com
Not an official Shimano STEPS document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.