1998 Subaru Legacy Owner's Manual - Page 110

If this light comes on steadily or blinks while the engine is running, it may indicate that there is a problem or potential problem somewhere in the emission control system. B If the light comes on steadily: If the light comes on steadily while driving or does not go out after the engine starts, an emission control system malfunction has been detected. You should have your vehicle checked by an authorized SUBARU dealer immediately. NOTE This light also comes on in the following cases: D The fuel tank is completely empty. D The fuel filler cap is not tightened until it clicks. If the fuel tank is empty, refill the tank as soon as possiblle. If you have recently refueled your vehicle, the cause of the CHECK ENGINE warning light/malfunction indicator lamp coming on could be a loose or missing fuel filler cap. Remove the cap and retighten it until it clicks. Make sure nothing is interfering with the sealing of the cap. Tightening the cap will not make the CHECK ENGINE warning light turn off immediately. It may take several driving trips. If the light does not go out, take your vehicle to your authorized SUBARU dealer immediately. B If the light is blinking: If the light is blinking while driving, an engine misfire condition has been detected which may damage the emission control system. To prevent serious damage to the emission control system, you should do the following: D Reduce vehicle speed. D Avoid hard acceleration. D Avoid steep uphill grades. D Reduce the amount of cargo, if possible. D Stop towing a trailer as soon as possible. The CHECK ENGINE warning light may stop blinking and come on steadily after several driving trips. You should have your vehicle 3-10