I have read around and found that replacing the black engine coolent temp sensor with the new green one, will help rid the P2181 code. I have done this with no problems, cleared the OBD2 code. The car runs fine, no different from before the sensor. For 3 days now no code came up until today, any clue on what to do next? Thermosat? Or just take it to the dealer? Engine temp is at steady 190 deg at normal running temp, car has about 66k miles on it. Its my gf's car, stock, and very easy driver with tons of freeway miles.