The invention relates to a method for controlling a powertrain system comprising an engine (2) and its pollution control system (4) for a compound from exhaust gases in which, during operation according to a predetermined mode: - a target content (S target_NOx) of the compound not to be exceeded at the exhaust line outlet is determined, - for each of the modes, the following are estimated: - the content of the compound produced by the heat engine, - the maximum efficiency (E) of the pollution control system, - the expected content of the compound downstream of the pollution control system, based on the expected content at the source and the efficiency (E), - the estimated contents for each of the modes are compared to the target content (S target_NOx) and, - among the modes for which the estimated content is lower than the target content (S target_NOx), the one that enables the lowest fuel consumption is applied.
