Shimano STEPS error E906: Inter-unit Communication Fault Detected
The system detected an irregularity in the data exchange between the display, battery, and drive unit. As a result, motor assist typically cuts off entirely and the bike will not power on or shuts down shortly after start-up. The code is stored in system memory and the warning indicator remains lit until cleared by firmware update or dealer tooling.
| Drive system | Shimano STEPS (E5000, E6100, E7000, E8000, EP6, EP801) |
| Severity | Dealer needed |
| Keep riding? | Ride with caution |
| Typical cost | A dealer firmware update with diagnostic is typically €30–60, a replacement wire harness €20–80, and a faulty battery or drive unit €500–900 depending on the model. |
Likely causes
- Outdated firmware on one or more components after a partial update or new unit installation
- Loose, dirty, or corroded connector at the battery, display, or drive unit
- Water ingress in the wire harness, junction box, or display port
- Battery firmware mismatch following a battery swap or replacement
- Failed component — battery, display, or drive unit — pulling the communication bus down
- Aftermarket or non-genuine part installed in the STEPS network
How to fix Shimano STEPS error E906
- Turn the system off and remove the battery from the frame.
- Inspect every visible connector between the display, battery, and drive unit for moisture, corrosion, or bent pins, then clean and re-seat them firmly.
- Refit the battery and confirm the charge level is above 50 percent before powering on.
- Install the E-TUBE PROJECT Cyclist app on a phone paired via Bluetooth, run the diagnostic, and update the firmware on every connected unit.
- If the app does not pair or the firmware will not load, take the bike to a dealer with the wired E-TUBE PROJECT tool.
- After the firmware update, perform a full power cycle and confirm the code has cleared before riding.
- If E906 returns with firmware current, the system has a hardware fault and a Shimano dealer must diagnose which unit is failing.
Warranty: Shimano's standard two-year warranty covers genuine component faults on STEPS systems but excludes water ingress, crash damage, and firmware issues introduced by non-genuine modifications.
Typical cost: A dealer firmware update with diagnostic is typically €30–60, a replacement wire harness €20–80, and a faulty battery or drive unit €500–900 depending on the model.
Frequently asked
Can I reset shimano error E906?
A power cycle (battery removed, wait 30 seconds, refit and power on) sometimes clears a transient glitch, but if the communication problem remains, E906 returns immediately. E906 is normally cleared by updating the firmware of every unit through E-TUBE PROJECT rather than by a manual reset.
Is it safe to keep riding with shimano E906?
No — the bike may drop assist without warning while riding, which is unsafe in traffic or mid-climb. Limit use to a short, flat ride directly to a dealer or stop riding until the fault is cleared.
How much does it cost to fix shimano E906?
A dealer firmware update plus diagnostic usually runs €30–60, but if a unit is genuinely faulty the part alone ranges from €100 for a harness to €500–900 for a drive unit or battery. Genuine component faults inside the two-year warranty window are normally covered; water ingress and crash damage are 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.