a few weeks a ago my blazer (01 xtreme) started running like crap. the temp gauge would drop all the way down like it wasnt reading and the the truck would rev up and/or stall out. then the gauge would start to read normally again and it would run just fine. after a few days of doing this the check engine light came on with the code P0118 coolant temp sensor circuit high input. yesterday i changed the sensor, now the it runs just fine but the check engine light is on and the temp gauge dont work. i inspected the pig tail when i swapped the sensor, its not corroded or have any wires exposed on it. any ideas on what could cause this?