The Subaru check engine light comes on when there is a problem with the Subaru’s emissions control system. The Subaru’s computer, called an ECU, generates fault codes that pertain to various sensors on the vehicle. If one of these sensors fails, it will trigger a fault code. The code is then stored in the computer until a diagnostic scan is run on the ECU to diagnose the problem. After the problem has been fixed, you’ll need to reset the “check engine” light.
Step 1: Open the hood of your Subaru and loosen the nut that holds the cable clamp to the negative battery terminal.
Step 2: Slide the cable off the negative battery terminal.
Step 3: Wait 5 minutes, then reconnect the cable and tighten the retaining nut. Start the engine and wait for the Subaru’s computer to reset the check engine light.