Assistance system for the regeneration of a NOx trap

Two lambda sensors (6, 7) are located at equal distances downstream of the nitrogen oxides (NOx) trap (3) in the exhaust line (2). One lambda sensor has a rhodium-based catalytic layer. Their output signals are connected to a differential measurement system (8), to determine the quantity of NOx in the exhaust gas. When the measurement exceeds a predetermined limit, the controller (4) initiates the regeneration phase.