How do I tell E012 from W013?

W013 appears immediately at startup and clears after a power cycle with foot off pedal. E012 either persists despite the power cycle procedure, or appears during riding rather than at startup. E012 indicates a more serious fault requiring mechanical investigation.

Can a new chain cause E012?

Yes. Installing a chain that is too tight or too loose for the specific STEPS drivetrain can cause E012 through chain tension affecting the motor housing. Always set chain tension according to Shimano STEPS specifications, not standard drivetrain practice.

Shimano STEPS Error E012: Torque Sensor Fault Fix

What Error E012 Means

Error E012 on Shimano STEPS systems signals a genuine torque sensor fault — not merely a startup calibration issue (which produces W013/W103). E012 means the torque sensor is returning out-of-range, implausible, or inconsistent data during riding, not just during startup initialisation. Motor assistance is disabled when E012 is active.

E012 and W013/W103 share the same underlying sensor but are triggered differently. W013 is a startup calibration miss; E012 is an ongoing signal fault during operation.

Common Causes

Pedal pressure at startup becoming E012 mid-ride — If W013 was not fully resolved and the bike was ridden, the torque sensor can escalate the warning to E012 as signal quality continues to be poor.
Chain tension issues — Incorrect chain tension on STEPS-compatible drivetrains transmits lateral force into the motor housing, producing spurious torque readings. This is most common after chain replacement.
Worn chainring — A worn or misshapen chainring creates uneven chain tension pulses that the torque sensor interprets as input spikes.
Loose crank arm — A loose crank arm creates flex that the torque sensor registers as rider input even when no force is applied.
Internal torque sensor failure — The strain gauge element inside the motor has failed after high mileage or impact.

Fix Procedure

Step 1: Startup Reset

Power off, stand clear of pedals, wait 10 seconds, power on. If E012 clears and does not return, the startup calibration was the root cause.

Step 2: Check Chain Tension and Wear

Use a chain wear indicator — Shimano recommends replacing the chain at 0.5 percent wear on STEPS drivetrains (earlier than the 0.75 percent standard for non-motor chains). Check that chain tension is even across the full rotation. Any stiff links or tight spots require chain replacement.

Step 3: Check Crank Arm Torque

Torque the crank arm bolt to specification — Shimano STEPS cranks use a hollow bolt design with specified torque of 34 to 44 Nm depending on model. A loose crank bolt is a confirmed cause of persistent E012.

Step 4: Firmware Update

Apply any available drive unit firmware via the E-Tube Project app. Known torque sensor calibration bugs have been corrected in multiple firmware updates for both E8000 and EP8 platforms.

Shimano STEPS Error E012: Torque Sensor Fault