The check engine light on a vehicle needs to be properly reset in order to turn off. A check engine light's purpose is to alert the driver of a problem with the drivetrain system. The safest way to reset the check engine light is to connect the computer to a diagnostic machine and troubleshoot the system.
Engine control modules, commonly referred to as ECMs, monitor the fuel, air and electrical sensors located on an engine. When one or more of these fail, the signals sent to the computer are obscured, which then releases a code from the system. One way to reset the check engine light is by using a diagnostics machine.
Locate the plug and set up the diagnostic machine
First locate the car's engine harness plug. Once found, set up the diagnostic machine to read the engine codes.
Scan the engine
Press the scan button so that the machine reads the car's error codes.
Clear the codes
Once the scan is done clear the codes; doing so turns off the check engine light.