Shimano STEPS error W935: Cycle computer lost link with drive unit
The cycle computer and the drive unit have stopped exchanging data over the wiring harness, and the system has flagged a communication error. Motor assist is cut, the displayed speed will not update, and walk assist is unavailable. The bicycle itself remains mechanically rideable, but only on leg power alone.
| Drive system | Shimano STEPS (E5000, E6100, E7000, E8000, EP6, EP801) |
| Severity | Warning |
| Keep riding? | Ride with caution |
| Typical cost | Dealer diagnostics typically cost €30–€60, a replacement Shimano cycle computer runs €80–€220 depending on model, and a full internal harness replacement if required is usually €60–€150 plus labour. |
Likely causes
- Display cable loose or unseated at the cycle computer mount.
- Damaged or chafed wiring harness between computer and drive unit.
- Corroded or wet pins in the cycle computer connector.
- Cycle computer internal board fault breaking the data link.
- Drive unit communication port damaged or contaminated.
- Previous crash or impact has disturbed the harness routing.
How to fix Shimano STEPS error W935
- Power off the system and remove the battery before any inspection.
- Unclip the cycle computer from its mount and inspect the connector pins for bend, dirt, or moisture.
- Clean the contacts with electrical contact cleaner and allow them to dry fully.
- Refit the computer firmly and confirm the cable sits without strain or kinks.
- Trace the visible cable run to the drive unit, looking for chafing, pinch marks, or crushed sections.
- Refit the battery, power on, and check whether W935 clears; if it returns, stop further home work.
- Take the bike to an authorised Shimano dealer for E-Tube diagnostics to isolate computer, harness, or drive unit fault.
Warranty: A genuine component failure of the cycle computer, harness, or drive unit inside the two-year Shimano warranty is normally covered, while damage from crashes, water ingress caused by pressure washing, or tampered wiring is excluded.
Typical cost: Dealer diagnostics typically cost €30–€60, a replacement Shimano cycle computer runs €80–€220 depending on model, and a full internal harness replacement if required is usually €60–€150 plus labour.
Frequently asked
Can I reset Shimano error W935?
Power the system off, remove the battery for around 30 seconds, then refit it and switch back on. If the underlying cable or connector fault is still present, the W935 code will return as soon as the system boots.
Is it safe to keep riding with W935?
The bicycle itself is mechanically rideable, but with no motor assist, no live speed reading, and no walk mode, treat it as caution only. Ride the shortest route home or to the workshop, and avoid steep climbs or busy traffic where loss of assist becomes a safety issue.
What does the W935 repair cost and is it under warranty?
Expect €30–€60 for dealer diagnostics and €80–€220 for a replacement cycle computer, with a wiring harness adding €60–€150 plus labour if needed. A genuine component failure inside the two-year Shimano warranty is normally covered, but crash damage or water ingress from pressure washing is not.
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.