Method of compensating for the effects of using a block heater in an internal combustion engine

1. Field of the Invention A method for determining the use of a block heater in an internal combustion engine and compensating for the effects that such heaters can have on an engine coolant sensor. The method uses measurements of ambient air temperature to determine if the use of a heater is likely and then compares the measured coolant temperature with an inferred coolant temperature to verify the usage of the block heater when the difference is significant. When use of a heater is detected, the value for coolant temperature initially supplied to the engine control system is compensated with a normalized coolant temperature value that is based on a functional relationship between the inferred engine temperature and the measured coolant temperature. Then as the mechanism of the engine begins to mechanically turn and the coolant is circulated, the normalized value of coolant temperature is filtered in a way that the normalized value approaches the temperature reading from the coolant sensor, as the starting process continues.