Abstract: The invention relates to an auxiliary unit included in a control arrangement for an internal combustion engine. An NTC-resistor (6) which is subjected to the effect of engine temperature of engine cooling-water temperature, is connected to a control system (5) which monitors the resistance of the NTC-resistor (6), this resistance varying with engine temperature, and utilizes this variation in resistance to change temperature-dependent control parameters for engine operation. The auxiliary control unit is connected to NTC-resistor (6). The auxiliary control unit applies an elevated voltage across the NTC-resistor over a predetermined period of time after an engine cold start, so as to deceive the control system (5) in indicating that the resistor is colder than it actually is.