1. Disconnect the battery. This will clear all of the ECM's memory, including any stored trouble codes.
2. Wait at least 10 minutes. This will allow the ECM to completely discharge.
3. Reconnect the battery.
4. Start the engine and let it run for at least 5 minutes. This will allow the ECM to re-learn its basic settings.
5. Turn the engine off and on again. This will verify that the ECM has been reset.
If you are still experiencing problems with your Forester's ECM, you may need to have it professionally diagnosed and repaired.