Malfunction indicator lamp (MIL / Check Engine)
Definition
The MIL is the amber engine-outline lamp in the instrument cluster that the ECU switches on when an emission-related fault has been confirmed; it is required by OBD-II and EOBD and must light briefly as a bulb check when the ignition is switched on. A steady lamp means a confirmed stored code: the car can usually be driven but should be diagnosed soon. A flashing lamp means misfires severe enough to overheat and destroy the catalytic converter, and the car should be stopped or driven very gently. The lamp turns off automatically after three consecutive fault-free drive cycles, or immediately when codes are cleared, but the fault memory and permanent codes remain. Diesel-only warnings (glow plug coil symbol) and the red oil or coolant lamps are separate; a MIL with no codes in generic OBD usually means a manufacturer-specific code that needs an enhanced scan tool. Codes: any confirmed P0xxx/P2xxx emission code, P0650 (MIL control circuit), P069E/P0656 (lamp request from another module).