1997 Subaru Legacy GT-check engine light

First off, you need to understand what that light means. When the light comes on steadily, it indicates that a problem has been detected with one or more of a large number of systems that are monitored by the ECU, and that a trouble code has been stored. When this happens it's ok to continue to drive the car until such time as you can have the code checked and any needed repairs made, although this should be done as soon as practical. However when the light FLASHES, it's a different story. This means that a real-time misfire is being detected, i.e. RIGHT NOW. This is something that must be addressed immediately as a sustained misfire can result in raw fuel being dumped into the catalytic converter, causing it to overheat and possibly sustain permanent damage. Possible causes of misfire are plugs, wires, coils, bad gas, burned/sticking valves, jumped valve timing, intake leak. You should have a shop look at it as soon as possible. In the case of a steady light where a code is stored, the light will go out on its own once the problem that set the code is no longer detected. The light can also be cleared using a scan tool, and the last method is to disconnect the battery. Note though that just clearing the code or doing a full ECU reset (which is what the battery disconnect does) won't fix anything that may be wrong so the light will likely come back on again unless the root cause is found and fixed. But when the light flashes there is no code to clear, it will continue to flash as long as the misfire condition exists. Only when the misfire stops or is repaired will the light go out. One other thing I should mention- if anyone happened to work on the car recently, and found two green plugs under the driver side dash that were just hanging and plugged them together, this would activate a diagnostic mode and make the light flash constantly. One way to tell if this is what happened is that the light will flash with the key in the "run" position even with the engine not running. In this case all you need to do is find the green plugs and disconnect them again.