Shimano STEPS error W020: Battery temperature outside operating range
The battery management system has detected that the battery pack is outside its guaranteed operating temperature window, either too hot or too cold. To protect the cells, Shimano cuts motor assist off completely and the bike rides like an unpowered bicycle. Walk assist also stops working until the pack is back inside the safe range.
| Drive system | Shimano STEPS (E5000, E6100, E7000, E8000, EP6, EP801) |
| Severity | Warning |
| Keep riding? | Ride with caution |
| Typical cost | A dealer diagnostic typically runs 30 to 60 EUR; a replacement Shimano battery, if confirmed faulty, ranges from roughly 450 EUR for the E5000/E6100 packs to 800 to 900 EUR for the larger E8000 and EP801 units, with labour for fitting and firmware pairing adding 40 to 80 EUR. |
Likely causes
- Battery left in direct sun or a hot car before a ride, pushing cell temperature above the upper limit.
- Sustained high-load riding in heat, such as long climbs, that heats the pack past the cutoff threshold.
- Riding or charging in sub-zero conditions that drop the pack below the lower operating limit.
- Restricted airflow around the battery mount, often from a packed pannier or mudguard blocking the casing.
- Failing temperature sensor inside the battery reporting an out-of-range value to the drive unit.
- Storing the bike in an unheated garage overnight in winter and attempting to ride immediately.
How to fix Shimano STEPS error W020
- Stop riding and switch the system off at the display to drop the load on the pack.
- Move the bike into shade or a moderate-temperature area, between roughly 10 and 30 °C.
- Let the battery rest for 20 to 60 minutes until the housing feels neutral to the touch; do not cool it with water.
- Clear any panniers, covers, or debris that are trapping heat against the battery casing.
- Power the system back on once the pack has stabilised and check whether the W020 reading has cleared on the display.
- If the code returns as soon as assist is requested, or the pack feels hot or icy without environmental cause, take the bike to an authorised Shimano dealer for a temperature-sensor and pack diagnostic.
Warranty: Environmental triggers such as riding in extreme heat or cold are treated as operating conditions and are not covered, whereas a defective battery thermistor or internal pack fault found inside the standard two-year warranty window is normally treated as a genuine component failure.
Typical cost: A dealer diagnostic typically runs 30 to 60 EUR; a replacement Shimano battery, if confirmed faulty, ranges from roughly 450 EUR for the E5000/E6100 packs to 800 to 900 EUR for the larger E8000 and EP801 units, with labour for fitting and firmware pairing adding 40 to 80 EUR.
Frequently asked
Can I reset Shimano error W020?
There is no manual reset button for this code. W020 clears on its own once the battery temperature sensor reports a value back inside the operating range. Power the system off, move the bike to a moderate environment, and wait for the reading to normalise before switching it back on.
Is it safe to keep riding with W020 active?
No, motor assist is cut and you will be pedalling an unpowered bike. Riding on is possible for a short distance on flat ground, but the battery is at a temperature that risks cell damage, so you should stop, let it recover, and address the cause before continuing.
Will Shimano replace the battery under warranty for W020?
Not on the strength of the code alone. If a diagnostic shows a genuine thermistor or pack fault within the two-year warranty period, Shimano typically covers the component. Heat or cold damage caused by storage and riding conditions is treated as wear and is billed to the owner.
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.