Its a code for a cooling system malfunction. Do you notice the car doesn't warm up to proper operating temp, like a stuck open thermostat? You might need to check it with a scanner that can read the data stream & watch the temp reading from the coolant temp sensor. It is the same unit that reads temp for the gauge in the dash, but a different part of the unit sends a measurement to the car's computer. Even if the gauge reads correct it may be giving a different reading to the ECM.