E-Bike Error Codes Explained: What the Number on Your Display Means
What e-bike error codes 21, 22, 25, 30, E10 and Bafang 04–30 mean, which ones you can clear yourself (brake sensor, throttle, loose connector) and when to stop riding and call service.
A number flashes on the display, the motor goes quiet, and the bike turns into a very heavy bicycle. The frustrating part is that the number means different things on different bikes: "21" is a motor-current fault on one display and a speed-sensor fault on another. This guide decodes the three code families used on most e-bikes sold in the US, tells you which faults you can clear yourself in five minutes, and which ones mean stop riding and get the bike to a technician.
The short answer
An e-bike error code is the controller reporting a sensor or wiring fault it can't work around. Most displays belong to one of three families: the 21 to 30 scheme (used on King-Meter and KD displays and on Whizz bikes), the Bafang scheme (04 to 49), and the KT scheme (01 to 06). Before you look anything up, do three things: turn the bike off and on, pull both brake levers and let them snap back, and make sure the throttle is at rest and every connector is clicked in. That clears the majority of brake-sensor, throttle and communication codes. If the code points at the motor hall sensor, a motor phase, the current sensor or overheating, or if it comes back after two restarts, stop riding. Updated October 2026.
First: which display do you have?
The same number can mean different faults, so identify the display family before you act.
| Family | Typical code range | How to recognize it | Bikes that use it |
|---|---|---|---|
| King-Meter / KD style (SW-LCD, KD21C, KD51C and similar) | 21, 22, 23, 24, 25, 30 | Codes start at 21; menu entered by holding "+" and "M"; parameters labelled P or C | Whizz Storm-2, Storm and Breeze; Rad Power Bikes; Ride1Up; many hub-motor commuter bikes |
| Bafang (DP C18, DP C240, E162/E163 and other Bafang displays) | 03 to 49, some with letters (4C) | "Bafang" or "BF" on the display or motor; codes shown with a wrench or "Error" text | Bafang mid-drive and hub-motor bikes from dozens of brands |
| KT (Kunteng) (LCD3, LCD5, LCD8HP) | 01_info to 06_info, plus "E" codes on generic displays | "KT" on the back of the display; errors shown as "0X_info"; parameters labelled C1 to C15 | Budget and conversion-kit bikes, many direct-import brands |
If none of these match, your manufacturer's manual is the only reliable source. Lectric, Aventon and other brands publish their own tables, and some reuse the numbers above with different meanings.
King-Meter / KD-style codes 21 to 30
This is the scheme Whizz bikes use, along with Rad Power Bikes, Ride1Up and other brands built around King-Meter or KD displays. The meanings come from the King-Meter SW-LCD manual; the self-checks are the ones dealers and brand support pages publish for these displays.
| Code | Meaning | Check yourself first | Needs a technician if |
|---|---|---|---|
| 21 | Abnormal current (the controller sees more current than it expects) | Switch off, let the motor cool for five minutes, switch on. Check the motor cable isn't pinched | The code returns under load, or you smell hot plastic |
| 22 | Throttle fault | Make sure the throttle is fully released when you power on; look for water or damage at the throttle and its connector | The code stays with the throttle unplugged, or the throttle is physically damaged |
| 23 | Motor phase problem | Common after a wheel removal: check the big motor cable is pushed fully in and the arrows on the connector line up | The connector is seated and the code persists |
| 24 | Motor hall sensor defect | Check the motor connector for bent pins or water | Almost always a motor or cable fault; don't ride on it |
| 25 | Brake failed (brake switch stuck on) | Pull each brake lever and let it return fully. If the code stays, unplug the left lever's connector, then the right, to find the stuck sensor | A lever's sensor is faulty and needs replacing; the mechanical brakes still work, the fault is the motor cut-off switch |
| 30 | Abnormal communication (display can't talk to the controller) | Power cycle. Then, with the power off, unplug and reseat every quick connector: display, controller, motor | Connectors are clean and seated and the code persists; usually a display, cable or controller fault |
On the Whizz Storm and Breeze, "abnormal communication" shows as code 9 rather than 30. Everything else in the table is the same.
Bafang codes 03 to 49
Bafang displays are the most common on mid-drive bikes and on many hub-motor bikes. The table below combines the DP C18 (UART) and the newer CAN-bus displays (DP C240, E162/E163); where the two generations differ, both meanings are given.
| Code | Meaning | What to do |
|---|---|---|
| 03 | Brake signal active (CAN displays) | Release the levers; check for a sticking brake cable or lever |
| 04 | Throttle not at rest at power-up | Release the throttle, power cycle |
| 05 | Throttle fault | Check the throttle connector for water or damage |
| 07 | Overvoltage (often a wrong or third-party battery) | Use the battery the bike shipped with; let a freshly charged battery sit a few minutes |
| 08 | Motor hall sensor fault | Technician |
| 09 | Motor phase fault | Technician |
| 10 | Motor over-temperature (CAN) | Stop, let the motor cool; the controller will cut power on its own if you keep going |
| 11 | Controller temperature sensor | Technician |
| 12 | Current sensor fault (check controller) | Technician |
| 13 | Battery temperature | Let the battery cool or warm to room temperature |
| 14 | Motor temperature (UART) or controller over-temperature (CAN) | Stop and cool down; if it repeats, technician |
| 21 | Speed sensor | Check the sensor magnet on the spoke is lined up with the sensor and not clogged |
| 22 | BMS communication (UART) | Reseat the battery; if it persists, the battery's electronics are at fault |
| 26 | Torque sensor (CAN) | Power on without touching the pedals; if it persists, technician |
| 30 | Communication fault | Power off, then check every connector for looseness, corrosion, bent pins or dirt (this is Bafang's own advice for code 30) |
| 36 | Power button held during start-up | Release the button, restart |
| 42 | Battery voltage low | Charge the battery |
| 49, 4C | Battery cell imbalance | Full charge; if it repeats, the battery needs service |
Note how the numbers collide with the first family: Bafang's 21 is the speed sensor, while King-Meter's 21 is motor current. Bafang's 22 is battery communication; King-Meter's 22 is the throttle. That is why the "which display" step matters.
KT display codes 01 to 06 and "E" codes like E10
KT (Kunteng) displays report faults with a small number and the word "info": 01_info is a throttle fault, 03_info motor hall sensor, 04_info torque sensor, 05_info speed sensor, and 06_info a motor or controller short circuit. The manual is blunt about resets: the display cannot leave the error screen until the fault is removed. The newer KT-LCD8HP writes the fault in words and returns to normal on its own once it is fixed.
What about E10? There is no manufacturer definition for E10 that we could find. On most generic displays (the S866 and similar), third-party guides describe E10 as a display-to-controller communication error. Treat it the way you would treat code 30: power cycle, then check every connector. But because "E" codes are not standardized, check your own manual before replacing anything.
The five-minute self-check that clears most codes
Do these in order. Switch the bike off before you unplug anything; Bafang's manuals warn that disconnecting under power can damage the electronics.
- Power cycle. Turn the display off, remove the battery, wait 30 seconds, refit the battery until it clicks, and turn the bike on with your hands off the brakes and throttle.
- Brake levers. Pull each lever fully and let it snap back. A lever that doesn't return (gritty cable, bent lever, ice) keeps the cut-off switch on and triggers a brake code.
- Throttle. It must sit at zero when you power on. Water in the throttle after rain or a wash is the usual cause of a throttle code; let it dry.
- Connectors. Trace the cable from the display to the controller and from the controller to the motor. Push every connector together until the arrows or markers line up. After a wheel change, the motor plug is the first suspect.
- Battery. Make sure it is seated and locked, charged, and not freshly out of the cold. A battery whose management system has cut out (low voltage, over-current, overheating) can look like a communication fault.
If the code disappears and stays away, you are done. If it comes back the first time you load the motor, treat it as a hardware fault. For problems that don't show a code at all, our electric bike troubleshooting guide covers power, wiring and mechanical issues, and there are separate guides for pedal assist not working and a battery that is fully charged but not working.
How to "reset" an e-bike display, and what a reset actually does
Every display family has a reset. On KT displays it is parameter C10; on KD51C displays it is the "DEF-00" option; Bafang calls it "Factory Setting"; Ride1Up's KD21C resets by holding "+" and "M" together. What none of them does is clear a fault. A factory reset restores the display's settings (wheel size, speed limit, assist levels, units) to their defaults. Error codes are generated by the controller every time it checks its sensors, so they disappear only when the sensor, cable or component is working again. No manufacturer manual says otherwise; the KD51C manual simply says to have the display repaired when an error code appears.
Two cautions. First, don't change the parameter menu to make a code go away. The settings that affect the controller (wheel size, current limit, speed limit) change how the bike behaves and can make it non-compliant: in New York City, for example, an e-bike offered for sale or rent must carry UL 2849 certification, and that certification covers the drive system, battery and charger as the combination that was tested. Our guide to UL 2849 battery safety explains what the standard covers. Second, don't open the battery or the controller. The battery management system cuts power on purpose when the pack is too low, too hot or over-current, and bypassing it is how fires start.
Codes that mean stop riding now
Some codes are the bike protecting itself. Riding through them risks the motor, the controller or you.
- Motor hall sensor or motor phase faults (King-Meter 23 and 24, Bafang 08 and 09). The motor can stutter, surge or lock. Bafang's manuals say to take the bike to the dealer for these.
- Current sensor faults (King-Meter 21 that returns, Bafang 12). The controller can no longer measure what it is sending to the motor.
- Overheating (Bafang 10, 11, 14). Stop and let it cool; if it repeats on a normal ride, the sensor or the motor is failing.
- Battery management faults (Bafang 22, 49, 4C). A cell imbalance or a BMS that can't talk to the controller is a battery problem, not a display problem.
- Anything with a smell or heat. Burnt plastic, melting insulation, a hot or swollen battery: stop, move the bike away from buildings, and don't charge it.
- A code that comes back after one or two restarts. At that point you are not troubleshooting, you are riding a faulty bike.
Riding with a motor-side fault on a delivery shift is the worst of both worlds: the bike is slower than a bicycle and may cut out in traffic. Walk it, or swap it.
Not an error: walk assist, speed limit and temperature icons
A few things look like faults and aren't. Holding the "down" or "minus" button for about two seconds starts walk assist: a flashing walk icon and the motor pushing the bike at up to about 6 km/h (4 mph). Release the button and it stops. A flashing or highlighted speed figure on some displays means you have hit the programmed speed limit, which is the bike working as designed. On KT displays, a flashing thermometer icon is a motor-temperature warning, not an error code: slow down and let the motor cool. And a display that shows nothing at all is usually a battery that isn't seated, a display that isn't switched on, or on Whizz bikes, a display that hasn't been unlocked with the key tag.
Whizz riders: what to do when a code shows
Whizz bikes use the 21 to 30 scheme in the first table. Your display may look slightly different from another rider's, because there are several display versions in the fleet, but the codes are the same. The rule from the Storm-2 manual is simple: when a code appears, stop riding and contact support.
| Code | Meaning on Whizz bikes | What to do |
|---|---|---|
| 21 | Current abnormal | Stop riding, contact support |
| 22 | Throttle abnormal | Stop riding, contact support |
| 23 | Motor phase problem | Stop riding, contact support |
| 24 | Motor hall defect | Stop riding, contact support |
| 25 | Brake failed (on Storm and Breeze: or brake applied while turning on) | Release both levers and power cycle once; if it stays, contact support |
| 30 (9 on Storm and Breeze) | Abnormal communication | Power cycle once; if it stays, contact support |
You don't need to troubleshoot a hardware code yourself. Text support at +1 (929) 685-1846 or message on WhatsApp at +1 (607) 600-9081, then bring the bike to any Whizz hub: repairs are walk-in, no appointment, and if the bike can't be fixed on the spot you get another one. Normal wear and tear is included in Rent-to-Own, with a service fee per visit. If you own your bike, WhizzCare Membership gives you the same workshops at member prices.
Frequently asked questions
What does error 25 mean on an e-bike?
On King-Meter and KD-style displays, including Whizz bikes, 25 means "brake failed": the brake cut-off switch is reporting that a lever is pulled. Release both levers and power cycle. If it persists, one lever's sensor is stuck or faulty. The mechanical brakes still work; the fault is only in the switch that cuts the motor.
What is error code E10 on an e-bike?
E10 has no standard manufacturer definition. On most generic displays it is reported as a communication error between the display and the controller. Power cycle the bike and check every connector, as you would for code 30, and confirm the meaning in your own manual.
How do I reset my e-bike display?
Each display has a factory reset (KT parameter C10, KD51C "DEF-00", Bafang "Factory Setting", or holding "+" and "M" on Ride1Up's KD21C). It restores settings, not sensors: an error code only clears once the fault behind it is fixed.
Can I keep riding with error 30?
Code 30 means the display and controller have lost communication, so the motor usually won't respond at all. Power cycle, then reseat every connector with the power off. If the code stays, the bike needs a technician; it's safe to pedal home without assist if the brakes work normally.
Why does the error come back after a reset?
Because the reset didn't touch the cause. A code that returns within a ride or two points to a damaged cable, a wet throttle or brake sensor, a failing motor sensor, or a battery problem. Stop troubleshooting and have it checked.
The bottom line
An error code is a fault report, not a glitch to clear. Identify your display family, do the five-minute check (power cycle, brake levers, throttle, connectors, battery), and if the code names the motor, the current sensor, overheating or the battery, or if it simply comes back, stop riding and get the bike serviced. On a Whizz bike, that means a text to support and a walk into the nearest hub.
Ride a bike that's serviced for you. The Whizz Storm-2 comes on Rent-to-Own with no credit check, walk-in repairs at any hub, and a replacement bike if yours can't be fixed on the spot.
Error codes vary by manufacturer and display version; the tables above are taken from the King-Meter, Bafang and KT manuals and from Whizz's own manuals, but always check the manual for your bike. Never open a battery or controller. Checked October 2026.