If you have ever searched an error code from your e-bike display and found the clearest answer on a different brand's support page, you were not imagining things. A large share of e-bikes report the same short list of two-digit codes — 21, 22, 23, 24, 25 and 30 — with nearly the same meanings.
The reason is unglamorous. Many brands build on controllers from the same upstream platform, and the code table came along with the hardware. Learn this one family and you can read a lot of displays that are not yours.
The shared six
21 — Current fault. The controller measured current outside its safe range and shut down to protect itself. It shows up most often on long climbs at maximum assist.
22 — Throttle fault. The throttle is not returning a signal the controller trusts.
23 — Motor phase. One of the three thick motor wires is not delivering power.
24 — Motor hall. The sensors that tell the controller where the motor is positioned are not reporting correctly.
25 — Brake sensor. A brake cut-off is being read as "applied" when it should not be.
30 — Communication. The display and the controller are not talking to each other.
Codes 23 and 24 tend to appear together because they share a home: the same motor cable carries both the phase wires and the hall wires.
Free checks before you buy any part
Most of these codes clear without a purchase, so work through the free checks first.
For 23 and 24, start at the motor cable connector near the chain stay. A partially seated 9-pin plug is the single most common cause, and reseating it costs nothing. Look for corrosion or water inside the plug while you are there.
For 25, try the simplest thing: release both brake levers fully and restart the bike. Many bikes latch this code if a lever is held at power-on. If it persists, unplug one brake sensor at a time to find which side is stuck.
For 22, check that the throttle returns smoothly and is not fouled by grit or pinched under a grip. Also check whether the display settings have limited or disabled the throttle — some displays include a walk-mode parameter that caps throttle speed, which reads as a fault to riders.
For 21, power down, let the bike cool for a couple of minutes, and restart. Then inspect the motor and controller cabling for chafing or dirt before assuming the controller failed.
For 30, inspect every cable between display and controller, especially where the harness bends at the head tube.
The exception that trips people up
The shared table is a strong pattern, not a law. Bafang-based systems are the common counterexample: there, 21 refers to a speed sensor problem and 25 refers to a torque signal error — different components entirely from the family above.
So confirm which system you are actually looking at before acting on a code. Guessing wrong here means buying the wrong part.
When it really is a part
If the free checks do not clear the code, the diagnosis usually narrows to one of three components: the motor, the controller, or the display.
A multimeter turns most of this from guesswork into measurement, and it is the one tool that pays for itself on the first repair. We stock a basic diagnostic multimeter for exactly this job.
For a persistent 30, the widely used replacement order is display first, then controller, then harness — the display is the cheapest of the three and a common failure point. One caution worth repeating: a controller and display generally have to be bought as a matched pair, because the protocol between them is the least interchangeable layer of an e-bike. Buying a display alone is where most cross-brand swaps fail.
If your bike shows no code at all but assist has stopped, the diagnosis runs differently — we covered that path in pedal assist not working while the throttle still does.
And if you ride a brand whose official support is no longer answering, the sourcing question is its own topic, which we wrote up in where to get replacement parts now.
Read the code, do the free checks, then buy the part you have actually confirmed.