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E-Bike Error Code Lookup

An e-bike error code only means something next to the system showing it: 21 is a speed-sensor fault on a Bafang display but “abnormal current” on a Rad, while 30 is a communication fault on both. Bosch 503 is the speed sensor. Shimano W103 means a sensor didn’t initialize — on an EP8 motor, turn the cranks backward two or three times. Bafang’s and Bosch’s first step for most codes is a restart.

No sign-up · works on your phoneUpdated 9 sources

Your display

The brand is usually printed on the display, the motor, or both.
Type it as shown — E21, 21 and Err 21 all work.

Common ones:

What it means

21 means 3 different things

It depends on the system. Pick yours on the left to narrow it down.
21BafangSensor

Speed sensor fault

The controller can't read wheel speed from the spoke magnet and sensor.

Try first: Restart. Check the spoke magnet lines up with the speed sensor, 10 to 20 mm apart, and that the sensor's connector is in. Then a BESST diagnostic, the sensor, and finally the controller.

Bafang: when a code appears, restart the system first; if it stays, see a dealer or technician.

Source: Bafang DP C244/C245 display user manual (July 2022) (opens in a new tab) · Bafang DP C18.UART display manual (copy hosted by bike43.com) (opens in a new tab) · Bafang error 04 service sheet (2022) (opens in a new tab)

Want a second opinion? Text a photo of the display with the bike’s make and model.

Worked example

Code 21 on three different vehicles

Bafang display: speed sensor fault — check the spoke magnet sits 10 to 20 mm from the sensor. Rad Power Bikes: abnormal current — Rad says stop riding and contact them. Segway-Ninebot Max scooter: battery (BMS) communication error. Same two digits, three different faults — which is why the lookup asks for the system, and shows every match when you’re not sure.

Reference

Every code, by system

Straight from each maker’s manual. Bafang · Bosch · Shimano STEPS · Rad Power Bikes · KT (Kunteng) · Segway-Ninebot scooter

Bafang error codes

A Bafang motor or Bafang display. The display model (DP C18, DP C244 and so on) is printed on its back. Bafang: when a code appears, restart the system first; if it stays, see a dealer or technician.

Bafang error codes: what each means and what to try first
CodeWhat it meansTry first
03Brakes enabled. The controller thinks a brake lever is pulled, so it cuts assist. Older UART displays such as the DP C18.Check that neither brake lever or brake cable is stuck.
04Throttle fault. The throttle has a fault. Bafang's separate service sheet for 04 describes a throttle that hasn't returned to its rest position.Check the throttle's cable and connector, then unplug and reconnect it. If it still won't work, the throttle needs replacing.
05Throttle not back in its rest position. The throttle isn't springing back to zero, so the controller won't trust it.Let the throttle return fully and check its connector. If it keeps happening, the throttle needs replacing.
07Overvoltage protection. The system saw a higher voltage than it allows.Remove and reinsert the battery. If it persists, Bafang points to a controller software update (its BESST tool), then the battery.
08Motor hall sensor signal fault. The sensors inside the motor that report its position aren't reading right.Check that every motor connector is seated. If it persists, Bafang's answer is the motor.
09Motor phase fault. A problem in the motor's phase windings or wiring.Bafang's answer is a new motor. Have the motor cable and connector checked before buying one.
10Motor at its maximum temperature. The motor has hit its heat limit — usually after a long climb. Keep riding and it cuts power.Switch off and let it cool. If it happens without a long climb, the motor needs looking at.
11Motor temperature sensor fault. The temperature sensor inside the motor has failed.Bafang: replace the motor.
12Controller current sensor fault. The sensor that measures current inside the controller has failed.Bafang: replace the controller.
13Battery temperature sensor fault. The temperature sensor inside the battery is reporting an error.Check the battery's connections to the motor. If it persists, Bafang points to the battery.
14Controller at its maximum temperature. The controller has reached its heat limit.Let the bike cool down and restart. If it persists, the controller.
15Controller temperature sensor fault. The temperature sensor inside the controller has failed.Let it cool and restart. If it persists, the controller.
21Speed sensor fault. The controller can't read wheel speed from the spoke magnet and sensor.Restart. Check the spoke magnet lines up with the speed sensor, 10 to 20 mm apart, and that the sensor's connector is in. Then a BESST diagnostic, the sensor, and finally the controller.
22Battery (BMS) communication fault. The controller isn't hearing from the battery's management system. Older UART displays such as the DP C18.Have the battery connection checked by a dealer or technician.
25Torque sensor signal fault. The torque sensor that measures how hard you pedal isn't giving a valid signal.Check every connection. A BESST check can read the torque signal; a controller update comes next, then the torque sensor.
26Torque sensor speed signal fault. The torque sensor's cadence (speed) signal has an error.Check the connections, try another display, update the controller with BESST; then the torque sensor.
27Controller overcurrent. The controller drew more current than it allows.Update the controller with BESST. If it persists, the controller.
28Torque sensor didn't initialize (warning). A warning, not an error: the torque sensor couldn't zero itself at start-up.Restart without pressing on the cranks.
30Communication problem. The display and controller (or other parts) aren't talking.Check every connector. Then a BESST diagnostic, a different display, a new EB-BUS cable, and reloading the controller software — in that order.
33Brake signal error. The brake sensor signal doesn't make sense to the controller. Bikes with brake sensors.Check the brake sensor connectors, then the brake levers, then the controller.
3515 V detection circuit fault. An internal power-supply check in the controller failed.Update the controller with BESST. If it persists, the controller.
36Keypad detection circuit fault. The controller's check of the button pad failed.Update the controller with BESST. If it persists, the controller.
37Watchdog circuit fault. The controller's internal watchdog (WDT) circuit is faulty.Update the controller with BESST. If it persists, the controller.
41Battery voltage too high. The battery's total voltage is above the limit.Bafang: replace the battery. Stop charging it until it's checked.
42Battery voltage too low. The battery's total voltage is below the limit.Charge it. If it persists, Bafang points to the battery.
43Battery cell power too high. The battery reports its cells' total power above the limit.Bafang: replace the battery.
44Single cell voltage too high. One cell group in the battery is over its voltage limit.Bafang: replace the battery. Stop charging it until it's checked.
45Battery too hot. The battery is over its temperature limit.Let the bike cool. If it persists, Bafang points to the battery.
46Battery too cold. The battery is under its temperature limit.Bring the battery to room temperature. If it persists, the battery.
47Battery state of charge too high. The battery reports a charge level above its limit.Bafang: replace the battery.
48Battery state of charge too low. The battery reports a charge level below its limit.Bafang's table says replace the battery. Charging it fully first rules out a flat pack.
61Gear shift detection fault. The system's shift detection isn't working.Check the gear shifter isn't jammed. If it is faulty, replace it.
62Electronic derailleur can't release. The electronic derailleur is stuck.Bafang: replace the derailleur.
71Electronic lock jammed. The bike's electronic lock is stuck.Update the display with BESST; then the display; then the lock.
81Bluetooth module error. The display's Bluetooth module has failed.Reload the display software with BESST. If it persists, the display.

Source: Bafang DP C244/C245 display user manual (July 2022) (opens in a new tab) · Bafang DP C18.UART display manual (copy hosted by bike43.com) (opens in a new tab) · Bafang error 04 service sheet (2022) (opens in a new tab)

Bosch error codes

A Bosch drive unit. Codes are three digits; this table is from Bosch's Purion display instructions. Bosch: you can keep riding without assistance, but have the bike checked before any more journeys.

Bosch error codes: what each means and what to try first
CodeWhat it meansTry first
410, 418Buttons disabled. One or more buttons on the on-board computer (410) or the operating unit (418) are stuck.Check for stuck buttons — dirt is the usual cause — and clean them.
414Operating unit connection problem. The handlebar remote isn't connecting.Have the connections checked.
419, 531, 593Configuration error. The system's configuration doesn't check out.Restart the system. If it persists, have the bike checked.
422Drive unit connection problem. The display can't reach the motor.Have the connections checked.
423Battery connection problem. The system can't reach the battery.Have the connections checked.
424Communication problem between components. Parts of the system aren't talking to each other.Have the connections checked.
426Internal time-out error. An internal time-out. While it shows, the wheel circumference can't be viewed or changed.Restart the system. If it persists, have the bike checked.
430On-board computer's own battery is flat. The display's internal battery has run down (not on the BUI350).Charge the on-board computer in its holder or over USB.
431, 580Software version error. Software versions don't match.Restart the system. If it persists, have the bike checked.
440, 500, 511Internal drive unit fault. The motor reports an internal fault.Restart the system. If it persists, have the bike checked.
450Internal software error. An internal software error.Restart the system. If it persists, have the bike checked.
460USB port error. A fault at the display's USB port.Unplug the cable from the on-board computer's USB port. If it persists, have it checked.
490Internal fault in the on-board computer. The display itself has a fault.Have the on-board computer checked.
502Bike light fault. A fault in the lights or their wiring.Check the light and its wiring, then restart.
503Speed sensor fault. The speed sensor has a fault.Restart the system. If it persists, have the bike checked. (504 is the one for a misplaced spoke magnet.)
504Speed signal distortion detected. The speed signal looks wrong — a moved spoke magnet, or tampering (tuning). Assist is reduced.Check the spoke magnet is positioned correctly and adjust it. Check nothing has been tampered with.
510Internal sensor fault. An internal sensor has a fault.Restart the system. If it persists, have the bike checked.
530Battery fault. The battery reports a fault.Switch off, remove the battery and put it back, then restart.
540Temperature error. The e-bike is outside its allowed temperature range.Switch off and let the drive unit cool down or warm up, then restart.
550Unapproved electrical load. Something is drawing power from the system that it doesn't allow — an unapproved accessory, for example.Remove the load and restart.
591Authentication error. A component failed the system's authentication check.Switch off, remove the battery and put it back, then restart.
592Incompatible component. A part — usually the display — isn't compatible with the system.Use a compatible display.
595, 596Communication error. Communication with the drive has failed.Check the wiring to the drive and restart.
602, 603, 640Internal battery fault. The battery reports an internal fault.Restart the system. If it persists, have the bike checked.
605Battery temperature error. The battery is outside its allowed temperature range.Switch off and let the battery cool down or warm up, then restart.
606External battery fault. A fault outside the battery — its wiring or connection.Check the wiring and restart.
610Battery voltage error. The battery voltage is out of range.Restart the system. If it persists, have the bike checked.
620Charger fault. The charger is faulty.Replace the charger — stop using this one.
655Multiple battery faults. The battery reports several faults at once.Switch off, remove the battery and put it back, then restart.
656Software version error. The software needs updating.Have a Bosch dealer update the software.
7xxThird-party component error. Any code in the 700s comes from a part Bosch didn't make, such as some lights or shifting.See that component maker's instructions.

Source: Bosch Purion original operating instructions (1 270 U20 XBP, 2020) (opens in a new tab)

Shimano STEPS error codes

A Shimano STEPS drive unit. Codes start with W (warning) or E (error); these come from the E7000 and EP8-era (SC-EM800) manuals. Shimano: a W warning clears itself once the cause is fixed; most E errors switch assist off until then.

Shimano STEPS error codes: what each means and what to try first
CodeWhat it meansTry first
W010Drive unit hotter than normal (warning). Assist may be reduced until the motor cools. E7000-era systems.Stop using assist until the drive unit cools.
W011Riding speed can't be detected (warning). The maximum assist speed may be lower than normal. E7000-era systems.Check the speed sensor is installed correctly.
W013Torque sensor didn't initialize (warning). The torque sensor couldn't zero itself at start-up, so assist may be weaker. E7000-era systems.Restart with your feet off the pedals.
W101No speed signal from the speed sensor (warning). The maximum assist speed drops below normal.Check the speed sensor and its magnet are installed in the right places.
W103Sensor initialization didn't complete (warning). Assist will be lower than normal.On a DU-EP800 drive unit, turn the cranks backward two or three times.
W104Power switched off: current leakage detected (warning). The system cut power because it detected current leaking somewhere. No assist.Have a shop remove components one at a time to find the faulty one.
W105Unexpected power disconnection (warning). Power dropped out unexpectedly.Restart. Stop the battery rattling in its mount, and check the power cord for damage.
W200, W020Battery outside its temperature range (warning). Power was switched off because the battery is too hot or too cold. Older units show W020.Too hot: leave the battery somewhere cool, out of the sun. Too cold: let it warm up.
W302, W032Shifting unit doesn't match the settings (warning). The shifting installed differs from what the system is set up for — for example an electronic derailleur fitted where a mechanical one was configured. Older units show W032.Have a shop check the setup in Shimano's E-TUBE PROJECT.
E010Drive unit / system abnormality. The system detected a fault; no assist.Switch off with the battery's power button and restart. If it persists, have it checked.
E020Battery–drive unit communication error. The battery and motor aren't talking; no assist.Have the cable between the drive unit and battery checked.
E021Battery not supported by this system. The battery meets the standard but this system doesn't support it; no assist.Restart with the battery's power button.
E022Battery doesn't meet the system's standard. Everything shuts down.Restart with the battery's power button. If it persists, have it checked.
E023Electrical failure inside the battery. Everything shuts down.Restart. If it persists, have the battery checked — don't keep charging it.
E024Battery overcurrent protection. The battery tripped its overcurrent protection. Everything shuts down.Use a genuine Shimano battery and check the power cord.
E025Battery doesn't recognize the drive unit. No genuine drive unit connected, or the power cord is disconnected. Nothing starts.Check the power cord and that genuine Shimano parts are fitted.
E030Shifting unit differs from the configuration. No assist until the configuration matches.Have a shop update the configuration in E-TUBE PROJECT.
E033Firmware not supported by this system. No assist.Update every unit's firmware to the latest in E-TUBE PROJECT.
E034, E013Drive unit firmware abnormality. The motor's firmware has a fault; no assist. Older units show E013.Have a shop restore the firmware in E-TUBE PROJECT.
E035Vehicle settings abnormality. No assist.Have a shop check and correct the settings in E-TUBE PROJECT.
E043Cycle computer firmware may be damaged. No assist.Have a shop restore the display's firmware.
E050, E014Abnormal speed sensor signal. The speed signal is wrong — often a sensor or magnet in the wrong place. No assist. Older units show E014.Install the speed sensor and magnet correctly; return a modified bike to its factory settings; then ride a short way to clear it.

Source: Shimano STEPS E7000 series user manual (opens in a new tab) · Shimano STEPS SC-EM800 user manual (opens in a new tab)

Rad Power Bikes error codes

A Rad Power Bikes e-bike. This list is from the RadRover manual; check your own model's manual if the code isn't here. Rad: if any error code shows, stop riding and contact Rad Power Bikes.

Rad Power Bikes error codes: what each means and what to try first
CodeWhat it meansTry first
21Abnormal current. The system measured a current it doesn't expect.Rad: stop riding and contact Rad Power Bikes.
22Throttle fault. The throttle signal is faulty.Rad: stop riding and contact Rad Power Bikes.
23Motor phase fault. A fault in the motor's phase wiring.Rad: stop riding and contact Rad Power Bikes.
24Motor hall fault. The motor's position sensors aren't reading right.Rad: stop riding and contact Rad Power Bikes.
25Brake switch fault, or brake pulled at power-on. A brake lever's cut-off switch is faulty — or a lever was squeezed while the bike switched on.Switch off, make sure neither brake lever is pulled, and switch on again. If it stays, Rad says stop riding and contact them.
30Communication fault. The display and controller aren't talking.Rad: stop riding and contact Rad Power Bikes.

Source: Rad Power Bikes RadRover owner's manual (opens in a new tab)

KT (Kunteng) error codes

A KT-LCD display, common on budget and kit e-bikes. Codes show as a number followed by "info". KT: the code stays on the display until the fault is fixed.

KT (Kunteng) error codes: what each means and what to try first
CodeWhat it meansTry first
01Throttle abnormality. The throttle signal is out of range.Check the throttle returns fully and its connector is seated.
03Motor hall signal abnormality. The motor's position sensors aren't reading right.Check the motor cable and connector for damage.
04Torque sensor signal abnormality. The torque sensor signal is out of range.Check the torque sensor's connector.
05Axle speed sensor abnormality. The torque sensor's speed signal is faulty. Torque-sensor bikes only.Check the sensor's connector.
06Short circuit in the motor or controller. A short circuit in the motor or controller.Stop riding and have it checked — don't keep powering a shorted system.

Source: KT-LCD3 product user manual (Suzhou Kunteng Electronics) (opens in a new tab)

Segway-Ninebot scooter error codes

A Segway-Ninebot kick scooter. This list is for the Max; other models may differ.

Segway-Ninebot scooter error codes: what each means and what to try first
CodeWhat it meansTry first
10Dashboard–controller communication fault. The dashboard and controller aren't talking.Restart, then have the dashboard connector reseated and the firmware updated.
11, 12, 13Motor phase current sensing fault. The controller can't measure current in one motor phase (11 = A, 12 = B, 13 = C).Have the phase wiring inspected; the controller is replaced before the motor.
14Throttle hall sensor fault. The throttle's sensor is reading wrong.Check the throttle moves freely and returns; then its wiring.
15, 16Brake hall sensor fault. The left (15) or right (16) brake lever's sensor is reading wrong.Make sure the brake isn't squeezed at power-on; check the lever's magnet and wiring.
18Motor hall sensor fault. The motor's position sensors aren't reading right.Have the motor's hall connector inspected; controller before motor.
19Abnormal battery voltage. The battery voltage is out of range.Charge the battery and check the charger.
21Battery (BMS) communication error. The controller isn't hearing from the battery.Charge it and have the battery connector checked.
22, 23, 27, 35Battery or controller not recognized. Password or serial-number mismatch between battery and controller (22, 23, 27, 35) — typically after one of them has been swapped.Needs Segway service tooling, or matched parts.
24System voltage detection fault. The controller's voltage reading is abnormal.Check for a firmware update or an overcharged battery; then battery or controller.
26, 31Controller memory or program error. A flash-save (26) or program-jump (31) error in the controller.Restart and update the firmware; the controller if it persists.
39Battery temperature sensor fault. The battery's temperature reading is abnormal.Let the battery warm up or cool down; replace it if the code stays.
40Controller temperature sensor fault. The controller's temperature reading is abnormal.Let it cool; replace the controller if the code stays.
41Motor temperature fault. The motor's temperature is abnormal.Let it cool; have the motor checked if the code stays.

Source: Levy Electric, Segway Max error code reference (2026) (opens in a new tab)

How to use it

In 4 steps

  1. 1Find the brand on the display or the motor and pick it. Not sure? Leave it on "Not sure" and it searches every system.
  2. 2Type the code as shown — E21, 21 and Err 21 all work. Shimano codes need their W or E.
  3. 3Read what it means and the maker's first step. Restart before anything else, unless the maker says to stop riding.
  4. 4A battery, charger or short-circuit code is the one not to push through: stop charging and riding until it's checked.

Why the same number means different things

There’s no industry standard for e-bike error codes. Each drive-system or display maker numbers its own faults: Bafang uses two digits, Bosch three, Shimano a W or E plus three digits, and KT’s displays a number followed by “info”. So a forum answer for “error 21” is only right if it’s about the same system as yours.

The makers’ own first steps are often simple — restart, check a connector, let the motor cool, realign the spoke magnet — and “replace the part” comes last, after those. That order matters when a code appears: a restart and a look at the obvious connection cost nothing.

The exceptions are codes that point at the battery or charger: over-voltage, a cell out of range, a charger fault, a short circuit. Stop charging and riding until it’s been looked at — the battery safety page covers the warning signs.

FAQ

Error codes: questions

What does error 21 mean on an e-bike?

It depends on the system. On a Bafang display, 21 is a speed sensor fault — check the spoke magnet lines up with the sensor, 10 to 20 mm apart. On a Rad Power Bikes display, 21 is abnormal current, and Rad says stop riding and contact them. On a Segway-Ninebot Max scooter, 21 is a battery (BMS) communication error.

What does error 30 mean on an e-bike?

A communication fault — the display and controller aren't talking — on both Bafang and Rad Power Bikes displays. Bafang's steps: check every connector, run a diagnostic with its BESST tool, try another display, replace the EB-BUS cable, and reload the controller software.

What does Bosch error 503 mean?

Speed sensor fault. Bosch says restart the system and, if it persists, see a Bosch dealer. Code 504 is the related one for a speed signal that looks wrong — check the spoke magnet's position and that nothing has been tampered with; assist is reduced until it's fixed.

What do Shimano W103 and W013 mean?

Both mean a sensor didn't initialize at start-up, so assist is weaker. On older STEPS systems (W013), restart with your feet off the pedals. On EP8-era systems (W103), Shimano says turn the cranks backward two or three times on a DU-EP800.

What does error 10 mean?

On a Bafang display, 10 means the motor has hit its maximum temperature — usually on a long climb — so stop and let it cool. On a Segway-Ninebot Max scooter, 10 is a dashboard–controller communication fault. Shimano's E010 is a system abnormality: restart with the battery's power button.

Can I keep riding with an error code?

Bosch says you can ride on without assistance but should have the bike checked before any more journeys. Rad says stop riding and contact them for any code. Whatever the brand, don't ride or charge through a battery, charger or short-circuit code.

How do I clear an e-bike error code?

Fix the cause and it clears: KT's displays drop the code once the fault is removed, and Shimano's warnings disappear once resolved. Bafang says to restart the system first whenever a code appears.

Something not answered here? Just ask — I’d rather talk it through than have you guess.

(949) 891-5278Send it in writing

Sources

Where these numbers come from

  1. [1]Bafang: Bafang DP C244/C245 display user manual (July 2022) (opens in a new tab)Error codes 04–81 and warn code 28, with Bafang's troubleshooting steps.
  2. [2]Bafang: Bafang DP C18.UART display manual (copy hosted by bike43.com) (opens in a new tab)Older UART display codes, including 03 (brakes enabled) and 22 (BMS communication).
  3. [3]Bafang: Bafang error 04 service sheet (2022) (opens in a new tab)04: the throttle has not returned to its correct position.
  4. [4]Bosch: Bosch Purion original operating instructions (1 270 U20 XBP, 2020) (opens in a new tab)Troubleshooting table, codes 410–656 and 7xx, as printed in Surly's Skid Loader manual.
  5. [5]Shimano STEPS: Shimano STEPS E7000 series user manual (opens in a new tab)Older codes: W010, W011, W013, W032, E010, E013, E014, E020–E022, E033, E043.
  6. [6]Shimano STEPS: Shimano STEPS SC-EM800 user manual (opens in a new tab)EP8-era codes W101–W302 and E010–E050, with the older equivalent in brackets.
  7. [7]Rad Power Bikes: Rad Power Bikes RadRover owner's manual (opens in a new tab)Codes 21, 22, 23, 24, 25 and 30.
  8. [8]KT (Kunteng): KT-LCD3 product user manual (Suzhou Kunteng Electronics) (opens in a new tab)Codes 01, 03, 04, 05 and 06.
  9. [9]Segway-Ninebot scooter: Levy Electric, Segway Max error code reference (2026) (opens in a new tab)A fleet operator's service reference for the Segway Ninebot Max; rental-only codes left out.

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