When the mechanic seen the engine warning light on on my dash he failed the truck.He did a code check and it was code P1281 which is due to the engine running to cold so it says.The truck was hot when it went in ?The heat works fine as well ? Now thats it in the dat base as a fail do I need to bring it to a shop or can I fix it myself ? I will see if I can reset the code.O r I will change out the thermostat.Any suggestions/ This was done in MA