What W011 / W101 Means

Error W011 on Shimano STEPS motors (E-series) and its equivalent W101 on the EP8 and EP801 platform signals that the drive unit is not receiving a valid speed reading from the speed sensor. The sensor is mounted on the chainstay and reads a magnet attached to a rear wheel spoke. Without a valid speed signal the motor cannot enforce the legal 25 km/h assist cutoff, so it reduces assistance and displays the warning.

W011/W101 is a warning code — motor assistance is limited but not fully disabled. The bike is still rideable at reduced speed.

EP8 vs E8000 codes: W011 applies to older E-series motors (E5000, E6100, E7000, E8000). The EP8 and EP801 use W101 for the same fault. Both are fixed the same way — only the code number differs between platform generations.

Common Causes

  1. Spoke magnet out of position — The magnet has slipped along the spoke or been knocked sideways by impact.
  2. Sensor gap too large — The gap between sensor face and passing magnet must be 3 to 17 mm. Outside this range the sensor cannot reliably detect the magnet.
  3. Dirty sensor or magnet face — Mud coating either component attenuates the signal below detection threshold.
  4. Damaged or pinched sensor cable — The thin two-wire cable from sensor to motor is vulnerable to cable-tie crushing and grommet fatigue.
  5. Rear wheel recently removed — Wheel removal shifts the axle slightly, changing the magnet-to-sensor gap.

Fix Procedure

Step 1: Locate the Spoke Magnet

Spin the rear wheel and watch the spoke magnet pass the sensor. The magnet should pass directly in front of the sensor face — not rotated sideways. If it has twisted, loosen the securing bolt or cable tie, align the flat face toward the sensor, and retighten.

Step 2: Measure the Air Gap

The correct gap between the sensor face and the magnet at closest approach is 3 to 17 mm. Use a feeler gauge, ruler, or stacked business cards to verify. If outside range, loosen the sensor bracket bolts, slide the bracket to achieve 5 to 10 mm gap, and retighten. Check gap after tightening — brackets can shift slightly.

Step 3: Clean Both Components

Wipe the sensor face and magnet face with a clean damp cloth. Dried mud can reduce effective magnetic signal by over 80 percent even with perfect alignment.

Step 4: Inspect the Sensor Cable

Trace the cable from the sensor body to its entry point on the motor. Look for pinch points under cable ties, abrasion against the frame, and tight bends near the grommet. Any section with a breached sheath requires cable replacement.

Step 5: Power Cycle

After making adjustments, power off completely, wait 10 seconds, and power on. W011/W101 should clear if the magnet is now producing a valid signal on every wheel rotation.