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.
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.
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.
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.
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.