A computer program, system and method are provided for thermally regulating an injector injecting a reducing agent into an exhaust pipe of an internal combustion engine. A pump is activated to deliver a coolant in a coolant circuit having a portion in heat exchange relation with the injector. A value is determined for a mass flow rate of the coolant delivered by the pump. A value is calculated for a temperature of the injector as a function of the determined value of the mass flow rate. A difference is calculated between the calculated value of the injector temperature and a predetermined set-point value thereof, and the mass flow rate of the coolant delivered by the pump is adjusted on the basis of the calculated difference.