A method is described for estimating the temperature of the exhaust gases upstream from a pre-catalyser (2) disposed along an exhaust pipe (7) of an internal-combustion engine (20), which is provided with a system (1) for controlling the composition of the exhaust gases, comprising an oxygen sensor (10), which is disposed along the exhaust pipe (7), upstream from the pre-catalyser (2), a heater (11), which is associated with the oxygen sensor (10), and a control unit (4), which, inter alia, serves the purpose of piloting the heater (11). The method comprises the steps of: determining an operative quantity (VPEFF), which is correlated to an electrical power (WE) supplied to the heater (11), in order to keep the operative temperature (TS) of the oxygen sensor (10) close to a target temperature (TO); and determining the temperature (TG) of the exhaust gases upstream from the pre-catalyser (2), according to the said operative quantity (VPEFF). IMAGE
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