SW900 Display Error Codes: The Complete Table and What Each One Means

Short answer: On an SW900, 0, 1, 4 and 5 are status messages, not faults. The fault codes are 2 (brake), 6 (low battery voltage), 7 (motor), 8 (throttle), 9 (controller), 10 and 11 (communication), 12 (battery management communication) and 13 (light circuit). Code 3 is listed for the pedal-assist sensor but marked not implemented in the manuals we checked. Most codes point at a connection before a part, so check the plug on that circuit first.

The SW900 is one of the most widely fitted displays in the aftermarket, and it numbers its codes differently from almost everything else. It starts at zero, and several of the numbers it shows are not faults at all — a detail that sends people hunting for parts they do not need.

Quick reference: SW900 codes 0 to 13

Unplug, reseat and inspect connectors with the bike switched off and the battery removed. Reconnect the battery and switch on only for the steps that need power, such as reading the code, a voltage reading, a reset or testing the throttle and pedal assist, and switch off again before you touch the next plug.

The SW900 is sold by many sellers and firmware varies between batches, so treat any number not listed here as unidentified. The Source column shows which manual lists each code. We cross-checked the meanings against King Meter's SW900 instruction sheet and a Sciwil S830 manual whose fault numbers overlap with the SW900's (it has no 11, and its 01 is reserved). For other displays and brands, see our e-bike error code lookup.

The numbers that are not faults

0 is normal operation. 1 is a save confirmation, shown when a setting has been written rather than when something has gone wrong. 4 means the six kilometre per hour walk mode is engaged, and 5 means cruise is engaged. If one of those four numbers is on screen, nothing is broken — leave the mode you are in and it clears by itself.

The codes that do mean something is wrong

2 — Brake. The controller is seeing a brake signal, either because a lever is being held or because a sensor is stuck on. Unplug the brake sensor connectors one at a time; if the code clears, you have found the stuck side.

3 — Pedal assist fault. The cadence sensor is not producing a signal the controller can read. Check the gap between the sensor and its magnet ring, check that the ring has not slipped on the axle, and clean both. A sensor that has drifted a couple of millimetres reads as a dead one.

A note on code 3: the King Meter SW900 and Sciwil S830 manuals we checked both mark it as not implemented, so we cannot confirm what a 3 means on your display. Treat the checks above as general pedal-sensor checks for when pedal assist has actually stopped working, not as a fix for the number itself.

6 — Battery voltage low. Charge it. If the code returns quickly on a pack that reads healthy at rest, the cause is more likely voltage sag under load than a display fault — a pack or a connection to look at, not a screen.

7 — Motor fault. Usually a hall signal the controller cannot read. Start at the nine-pin motor connector rather than at the motor: a bent or corroded pin looks exactly like a dead sensor from the controller's point of view. Our guide to phase and hall wiring colours covers which wires you are working with.

8 — Throttle fault. The throttle signal is out of range, most often because it is not returning to rest or because water got into the connector. Unplug it: if the code clears with the throttle disconnected, that is the part to replace, and one of the cheapest on the bike.

9 — Controller fault. An internal fault reported by the controller. Try a hard reset first — battery off for ten to fifteen minutes, not a quick cycle. A controller that keeps reporting it afterwards is one to replace.

12 — Battery management system communication. The controller and the pack's management board are not talking. Check the communication line and its connector before concluding the pack has failed — a cable can cause this one.

13 — Light fault. The light circuit is drawing current it should not, or the connection is shorted. Disconnect the headlight and see whether the code clears before looking further up the harness.

10 and 11: which direction failed

10 is a receive failure and 11 is a transmit failure, so the display is telling you which direction of the link went quiet rather than just that it is down. Both usually come back to the communication cable, its connectors, or moisture in one of them, and both deserve the same first step: unplug and inspect rather than buy. The distinction helps afterwards: a display that can still report a code still has power and a processor running, so once the cable and connectors check out, the controller end is generally the more likely one to have stopped. That beats replacing the screen just because the screen is where the number appeared.

Where these codes come from

This table is compiled from retailer documentation and owner forums, not from a manufacturer's service manual. The display is sold by many sellers under one model name, and firmware varies between batches. If a number appears that is not listed here, treat it as unidentified and diagnose by symptom — inventing a definition is how the wrong part gets ordered.

The compatibility trap behind the communication codes

A communication code on an SW900 is often not a failure at all. It is a mismatch. The SW900 belongs to the KT protocol family and uses a proprietary link that pairs with KT controllers; fit one to a controller from a different platform and the two will not talk, however neatly the plug fits. Connector shape is not protocol. If code 10 or 11 appeared right after a display or controller was swapped, look there first — we go through the whole problem in why a new display often will not work with your controller. For the same numbering logic on a related display, compare our KT-LCD code table.

Common questions

Why does my SW900 show 4 or 5 when nothing is wrong?

4 means the walk mode is engaged and 5 means cruise is engaged. They are status messages, so leave the mode you are in and the number clears by itself.

Should I replace the display for code 10 or 11?

Not first. Both point at the communication link: the cable, its connectors or moisture in one of them. A display that can still report a code has power and a running processor, so once the cable checks out the controller end is generally the more likely one. If the code appeared right after a swap, read why displays are not interchangeable.

Is code 7 always a dead hall sensor?

No. It reports a motor fault, and a bent or corroded pin in the nine-pin motor connector looks exactly like a dead sensor to the controller. Inspect the plug first, then follow our hall sensor test.

Getting from a code to a part

Every fault code above names a circuit, not a verdict. Codes 3, 7, 8 and 13 all point at a sensor, a lamp or its wiring, and the connector is more often at fault than the component behind it. Unplug it, inspect the pins, reseat it, and re-test before buying. A meter at the connector tells you whether signal is arriving, and that one measurement usually decides which part needs replacing.

A digital multimeter covers that measurement; if it confirms a failed sensor or throttle, compare connectors in our sensors and throttles collection before ordering.

Note the number, whether it appears constantly or only under load, and work the free checks first. Most SW900 codes are describing a connection, and the ones that are not will still be waiting once the connections have been ruled out.

If your code or symptom is not covered here, our e-bike repair online guide walks you from a three-minute self-check to the right part.

This guide is part of our e-bike error code lookup. Related: how to identify your display model, the hard reset guide and brake sensors and no-power faults.

Last updated November 4, 2026: added a short answer, a quick-reference table with a source for each code, answers to common questions and a note that the manuals we checked mark code 3 as not implemented.