The check engine light on a 1999 BMW 323 is controlled by the vehicle’s engine control module (ECM). The ECM illuminates the check engine light when it senses a malfunction related to the engine and its performance. Anything, from a faulty sensor to a cylinder misfire, can cause the ECM to display the check engine light. This warning light cannot be turned off without the use of a computerized scan tool.
Shut down the engine and place the vehicle in park or first gear (manual transmission). Engage the parking brake. Turn the ignition to the “ON” position but do not start it.
Locate the vehicle’s diagnostic computer port mounted underneath the dashboard on the driver’s side, just above the pedals.
Plug the scan tool’s data cord into the diagnostic port and power on the scan tool. Wait for the tool to establish communication with the vehicle.
Navigate to the “Codes” menu on the scan tool. Select “Read All Codes” and write down the information displayed on the scan tool. This diagnostic information will help to determine the problem that caused the check engine light to illuminate.
Select “Clear All Codes” on the scan tool. Wait for the check engine light to turn off.
Start the engine to make sure that the check engine light remains off.
