ECU / ECM (Engine Control Unit)

The ECU (engine control unit), also called ECM (engine control module), is a small computer that reads sensors – throttle position, engine speed, air temperature and pressure, coolant temperature, oxygen sensor – and decides how much fuel to inject and when to fire the spark.

On modern motorcycles it often also handles ride-by-wire throttle, riding modes, traction and wheelie control, quickshifters and diagnostics. Fault codes are stored and can be read with a diagnostic tool or sometimes via the dashboard.

Fitting an aftermarket exhaust or air filter may require an ECU remap or fuel module. Remapping can affect emissions compliance, type approval and warranty, so check before modifying. Keep connectors clean and dry; many “ECU faults” are really poor connections or a weak battery.