99 Nissan Altima - Warning light resetting

The service engine soon or AKA check engine light is giving you an indication that there is a problem with the cars engine control system ( O2 senors, EVAP system, Engine coolant temp senor ETC) The only way to clear it is with a scan tool. The tool will display a code telling where you should look for the problem. You can clear the code will the scan tool but if the problem still exist then the light will come back on. Good luck Backyardmechanic :o
PS some auto parts stores will extact the code for free.