Ebike error code reference — what every code actually means
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Your display shows E003, or Er 21, or Service. Manuals are cryptic. This reference lists every common code across the five major controller families used in UK/US ebikes — what it means, what to check first, and whether you can fix it or if it's dealer-only.
The problem
Generic ebikes use KT / Bafang / Das-Kit controllers with overlapping but non-identical error codes. Premium ebikes (Bosch, Shimano, Yamaha) use proprietary systems with their own error language. Misreading a code costs time and money — 'low voltage' gets treated as a dead battery when it's actually a loose connector.
Reference tools
AstroAI digital multimeter
Best for: Verifying voltage-related error codes
- Confirms E03/Err06 low voltage without guessing
- Auto-ranging DC
Bosch diagnostic tool (for DIY Bosch owners)
Best for: Reading Bosch codes without dealer
- USB-OTG tool reads Bosch drive errors
- Compatible with BUI300, BUI330, BUI350
Watch out: Third-party — no warranty. Use at own risk.
Generic OBD-style ebike diagnostic cable (KT/Bafang)
Best for: Reading/writing KT and Bafang controller parameters
- Connects via USB to PC
- Reads error history, adjusts parameters
Bafang controllers (most generic ebikes)
Bafang error codes
| Code | Meaning | Fix |
|---|---|---|
| E01 | Throttle abnormal — signal out of range at startup | Throttle fault or stuck. Replace throttle (see throttle flow). |
| E02 | Brake signal / brake sensor engaged at startup | Check brake levers aren't engaged. Brake sensor adjustment or replacement. |
| E03 | Low voltage — battery below cutoff | Charge battery. If persistent at full charge, cell-group imbalance (see multimeter test). |
| E04 | Motor hall sensor fault | Motor hall sensor dead or connector loose. Check motor cable, see motor flow. |
| E05 | Over-current / overload | Motor stalling under load. Gear down. If persistent, motor phase wire issue. |
| E06 | Overvoltage / charger fault | Wrong-voltage charger or faulty charger output. Verify with multimeter. |
| E07 | High current / short | Motor phase wire shorted. Check motor cable, disconnect and inspect for damage. |
| E08 | Communication error — controller/display | Display cable loose or damaged. Disconnect + reconnect. Replace cable if damage visible. |
| E09 / E10 | Motor overheat / thermal cutoff | Motor hit thermal limit. Cool, ride easier. Recurrent = consider external heatsink or higher-torque motor. |
| E11 | Controller overheat | Heat-soaked controller. Move to shaded spot, improve airflow. Persistent = controller replacement. |
| E12 | Current sensor fault | Internal controller fault. Usually requires controller replacement. |
| E21 | Current sensor fault | Same as E12 — shunt/sense resistor fault. |
| E25 | Brake signal abnormal | Brake sensor cut or stuck. Disconnect brake sensor wire — if bike works normally, confirmed fault. |
| E30 | Communication loss | Display-to-controller connection dropped. Typically connector corrosion or cable damage. |
KT display codes (KT-LCD3, LCD4, LCD5, LCD6, LCD8H)
KT error codes
| Code | Meaning | Fix |
|---|---|---|
| Err 01 | Current abnormal | Controller current sensor fault. Usually needs controller replacement. |
| Err 02 | Throttle self-check fault | Throttle not at rest position at power-on. Check throttle mechanism. |
| Err 03 | Motor hall sensor fault | Hall sensor dead or disconnected. Check motor cable. |
| Err 04 | Throttle fault | Throttle hall sensor failed. Replace throttle. |
| Err 05 | Brake sensor fault | Brake sensor stuck activated. Disconnect and test. |
| Err 06 | Low voltage | Battery low or cell-group imbalance. |
| Err 07 | High voltage | Wrong charger or charger over-volting. |
| Err 08 | Motor phase short | Motor phase wires shorted. Controller may have blown MOSFETs. |
| Err 21 / Err 22 | Controller communication | Display-controller cable loose or damaged. |
Bosch drive systems (Active, Performance, CX, Cargo Line)
Common Bosch codes
Bosch shows "Service" + a numerical code. Bosch codes are diagnostic — most require dealer software (BUI) to clear properly, but many indicate obvious physical faults you can address.
| Code | Meaning | Action |
|---|---|---|
| 500 / 501 | Battery cell voltage imbalance | Dealer service or replacement. |
| 502 / 503 | Battery temperature outside operating range | Let battery warm up (or cool down). Ride when at ambient temp. |
| 504 / 505 | BMS communication error | Remove + reseat battery. If persistent, battery needs dealer diagnostic. |
| 510 | Speed sensor error | Magnet + sensor misaligned. Check rear wheel spoke magnet and sensor gap. |
| 530 | Drive unit error | Internal drive fault. Dealer only. |
| 540 | Drive unit temperature | Motor overheating. Cool + ride easier. Recurrent = dealer check. |
| 550 | Display communication error | Cable between display and drive. Reseat connector. If persists, dealer. |
| 562 | Firmware update required | Dealer update. Free at authorised Bosch dealers. |
Shimano Steps (E6100, E7000, E8000, EP8)
Common Shimano codes
Shimano codes use format W013, E010, etc. W-codes are warnings (you can ride), E-codes are errors (often stop ride).
| Code | Meaning | Action |
|---|---|---|
| W011 | Drive unit communication | Reseat display cable. Power cycle. |
| W013 | Speed sensor | Check sensor-magnet alignment at rear wheel. |
| W101 | Battery error | Remove + reseat battery. Check battery connector for damage. |
| E010 | System error | Dealer diagnosis required. |
| E011 / E012 | Drive unit fault | Dealer-level. Warranty if recent. |
| E013 | Torque sensor calibration | Dealer re-calibration needed (uses E-tube software). |
Yamaha PW / PWseries C / PW-X2 / PW-X3
Common Yamaha codes
| Code | Meaning | Action |
|---|---|---|
| Err 21 | Drive motor communication | Reseat connectors. Warranty dealer if persists. |
| Err 22 / 23 | Drive motor internal | Dealer-only service. |
| Err 24 | Battery communication | Reseat battery. Check contacts for corrosion. |
| Err 25 | Torque sensor | Dealer re-calibration. |
| Er Low | Battery critically low | Charge battery fully. If persistent at full charge, cell issue. |
General clearing procedure
- Power off ebike completely. Remove battery.
- Wait 60 seconds (capacitors discharge).
- Reinstall battery, power on.
- If code persists: address specific fault per table above.
- Many generic codes auto-clear once the fault is resolved. OEM codes often require dealer software.
FAQ
Error clears itself when I power-cycle, then comes back — is that significant?
Yes — means intermittent fault. Usually a loose connector or cable partially broken internally. The code isn't the problem, it's a symptom.
Can I disable error codes to keep riding?
No — for safety reasons. Codes like E03 (low voltage) or E09 (overheat) protect the motor/battery from further damage.
Why does my ebike not show any error code but still not work?
No-code + no function usually = power delivery issue before controller — dead battery, blown fuse (some ebikes have an inline fuse near battery mount), or severed main power wire.
Do generic error codes match up with Bosch/Shimano codes?
No — each system uses its own code set. KT E03 (low voltage) means the same thing as Bosch 500 (cell imbalance) but not the same code. Match the ebike brand to the right table above.