Shimano STEPS error W031: Chain tension or crank position warning
The drive unit has detected that the chain is not at the correct tension or that the crank arm is not seated in its proper position on the spindle. As a result, the system limits or cuts motor assist to protect the drivetrain from further damage. The display will keep showing W031 until the mechanical condition is corrected and the system is restarted.
| Drive system | Shimano STEPS (E5000, E6100, E7000, E8000, EP6, EP801) |
| Severity | Warning |
| Keep riding? | Ride with caution |
| Typical cost | A workshop chain tension and crank check typically runs €25-€45, a single crank arm €40-€90, and a chain plus fitting €30-€70 depending on the group level. |
Likely causes
- Chain has stretched and dropped out of adjustment during normal use
- Crank arm bolt loose or not torqued to the Shimano specification
- Crank removed for transport or service and not pushed fully back onto the spindle
- Chainring bolts worked loose after a recent install or a hard hit
- Rear wheel sitting forward in the dropouts, reducing chain wrap
How to fix Shimano STEPS error W031
- Stop the bike, switch off the system, and remove the battery before any inspection.
- Visually check the chain for obvious slack and confirm both crank arms sit fully home on the spindle.
- Tighten the crank arm pinch bolts to the torque printed on the crank, typically 12-14 Nm.
- Re-tension the chain through the rear axle or the derailleur clutch as appropriate to the bike.
- Refit the battery, power the system on, and ride briefly to see whether W031 clears.
- If W031 returns or the crank cannot be fully seated, take the bike to an authorised Shimano dealer.
Warranty: Chain stretch, loose crank bolts, and crash damage are treated as wear or owner-maintenance items and are not covered, while a genuine crankset or motor-side sensor fault inside the two-year warranty period is normally replaced free of charge.
Typical cost: A workshop chain tension and crank check typically runs €25-€45, a single crank arm €40-€90, and a chain plus fitting €30-€70 depending on the group level.
Frequently asked
Can I reset Shimano error W031?
There is no rider-accessible reset for W031 because it is triggered by the drive unit sensing a mechanical condition rather than a software fault. The warning clears on its own once the chain is retensioned and the crank is correctly seated, and the system is powered back up.
Is it safe to keep riding with W031?
Riding is technically possible but not recommended, since the motor will cut or sharply reduce assist and you risk damaging the chainring, chain, or crank spindle. Get off the road at the next safe spot and inspect the drivetrain before continuing.
How much will fixing W031 cost and is it under warranty?
A simple chain tension and crank check usually costs €25-€45 and is treated as owner maintenance, since chain stretch and loose bolts are not warranty items. If the crank arm or a related motor sensor turns out to be genuinely defective inside the two-year warranty, Shimano typically covers parts and labour at no charge.
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.