Check engine light on. Took it to Autozone and my 2006 Civic threw the P0128 code. Car running fine. I replaced the thermostat. Check engine light still on. Will it turn off eventually or do I need to rest it, and if so how? If it wasn't the thermostat what else could it be? car has 150k miles and I don't want to spend bucks chasing a faulty signal if the car is running fine.