Abstract: A control system for regenerating a particulate trap in the exhaust system of a diesel engine includes control logic which controls the air/fuel ratio of the engine by operating a backpressure valve in the engine exhaust system to provide a proper amount of excess oxygen to permit efficient combustion of the particulate content of the trap, but to avoid rapid and damaging combustion rates. Actual engine air/fuel ratio is compared to a commanded air/fuel ratio, and the position of the backpressure valve is adjusted accordingly. The commanded air/fuel ratio is ratcheted upwardly or downwardly once in a predetermined time period in response to a temperature error signal between exhaust gas temperature sensed in the engine exhaust manifold and a predetermined commanded temperature.