The Mazda 6's engine light is designed to quickly alert the driver to failing drivetrain components. When the light comes on without reason, or refuses to turn off after the problem has been repaired, a manual reset is required. Since the light is controlled by the computer system, momentarily disconnecting the power supply will turn the light off, delete all stored error codes, and restore the system to a factory state.
Place the socket wrench over the nut on the negative battery cable and loosen it only until the cable is free to slide off. Do not fully remove the nut. Move the cable as far away from the battery as possible, to prevent it from springing back into place.
Turn the Mazda's headlights on. This will help to more quickly drain power from the computer. Wait 5 minutes, then turn the lights off.
Reconnect the battery cable, securely tightening the nut. Start the engine and check the dash to confirm the light has been reset.
Allow the engine to idle for 5 minutes before driving. This gives the engine management system a chance to recalibrate.
Disconnecting the battery will cause some digital settings, such as the clock, to be reset.