What W010 / W100 Means

Error W010 on Shimano STEPS E-series motors and W100 on EP8 / EP801 is an overtemperature warning. The motor contains internal NTC temperature sensors that monitor the motor windings and power electronics. When either sensor exceeds the thermal threshold, the system raises W010/W100 and progressively reduces motor output to prevent permanent damage.

This is a warning code, not an error — the motor does not shut down completely. Assistance is reduced proportionally to how far above the thermal threshold the motor is operating.

Cooldown Procedure

  1. Reduce assist level to Eco or Off immediately. Every watt of power assistance generates heat — cutting assist lets the motor cool while you continue moving.
  2. Shift to a lower gear and maintain a higher cadence (80 to 100 RPM). High cadence at low torque is the most thermally efficient pedalling mode.
  3. If assistance drops to zero and W010/W100 persists, stop and rest the bike in shade for 10 to 20 minutes.
  4. Do not pour cold water on the motor.
  5. Power off and back on after cooling. W010/W100 clears automatically when temperature drops below the reset threshold.

Prevention

The Shimano EP8 motor produces 85 Nm of torque and, under Boost mode on steep grades, generates considerable heat. The most effective prevention strategy is gear selection: on sustained climbs over 10 minutes, use Tour or Eco mode rather than Boost, and maintain 70 to 90 RPM cadence. This reduces motor torque output by 40 to 60 percent compared to high-gear Boost climbing, dramatically reducing heat generation.

The E-Tube Project app allows EP8 riders to cap maximum torque output — setting a lower torque limit for everyday riding reduces thermal load and extends the service life of the motor.