E-bike reference

42 e-bike error codes, explained in plain language.

What does the code on your display mean? Causes, roadside self-help and sources — for Bosch, Shimano STEPS, Yamaha and more. Free and maintained with love for the detail. Enjoy the ride!

Shimano STEPS Sensors

W103

Torque sensor initialization failed (EP8 generation)

The EP8-generation counterpart to W013: the torque sensor could not finish its self-calibration at startup, usually because the pedals were loaded when the system was switched on. Assist remains weaker than normal until initialization succeeds. Rotating the crank backwards a few times or restarting without pedal load normally clears the warning.

Drive system
Shimano STEPS
Category
Sensors
Motor behavior
assist reduced
DIY-friendly?
possible

Roadside self-help

  1. Rotate the crank backwards two to three times.
  2. Switch the system off and on again without touching the pedals.
  3. If the warning keeps returning, contact your dealer.

Possible causes

  • Load on the pedals while switching on high
  • Sensor self-calibration interrupted medium
  • Persistent torque sensor defect low

Symptoms

  • Weaker assist than usual right after startup
  • Warning shown on display or in the app

Inspection / repair

  • Difficulty: easy
  • DIY: possible

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Applies to

Sources

How to read e-bike error codes

Unlike cars (OBD-II), e-bike codes are manufacturer-specific: the same number means something different on a Bosch than on a Shimano system. What matters is always the combination of drive system and code.