A method for heating an exhaust pipe in a motor vehicle, comprising the steps of: - injecting a predetermined quantity of fuel and comburent into an injection area inside an exhaust pipe in a motor vehicle; - performing a plurality of spark cycles in succession, wherein each spark cycle comprises: - generating at least one spark between the ends of a pair of electrodes (7, 8) located in proximity to the injection area in order to start a combustion; - detecting the value of a representative quantity representing a ionization current flowing between said ends of the pair of electrodes (7, 8) following the extinction of said spark; - comparing said value of the representative quantity representing the ionization current with a preset reference value and determining: the presence of combustion in the spark cycle if said value of the representative quantity is greater than said preset reference value; the absence of combustion in the spark cycle if said value of the representative quantity is less than said preset reference value; - generating, in the same spark cycle or in a subsequent cycle, information relating to the absence or presence of combustion according to the outcome of said comparison. - injecting a predetermined quantity of fuel and comburent into an injection area inside an exhaust pipe in a motor vehicle; - performing a plurality of spark cycles in succession, wherein each spark cycle comprises: - generating at least one spark between the ends of a pair of electrodes (7, 8) located in proximity to the injection area in order to start a combustion; - detecting the value of a representative quantity representing a ionization current flowing between said ends of the pair of electrodes (7, 8) following the extinction of said spark; - comparing said value of the representative quantity representing the ionization current with a preset reference value and determining: the presence of combustion in the spark cycle if said value of the representative quantity is greater than said preset reference value; the absence of combustion in the spark cycle if said value of the representative quantity is less than said preset reference value; - generating at least one spark between the ends of a pair of electrodes (7, 8) located in proximity to the injection area in order to start a combustion; - detecting the value of a representative quantity representing a ionization current flowing between said ends of the pair of electrodes (7, 8) following the extinction of said spark; - comparing said value of the representative quantity representing the ionization current with a preset reference value and determining: the presence of combustion in the spark cycle if said value of the representative quantity is greater than said preset reference value; the absence of combustion in the spark cycle if said value of the representative quantity is less than said preset reference value; the presence of combustion in the spark cycle if said value of the representative quantity is greater than said preset reference value; the absence of combustion in the spark cycle if said value of the representative quantity is less than said preset reference value; - generating, in the same spark cycle or in a subsequent cycle, information relating to the absence or presence of combustion according to the outcome of said comparison.