Method for controlling regeneration within an after-treatment component of an engine comprises receiving an upstream temperature signal, receiving a downstream temperature signal, and calculating a temperature difference based on a difference between the upstream temperature signal and the downstream temperature signal. The temperature difference is compared to a predetermined temperature change limit to determine whether the temperature difference is less than or greater than the predetermined temperature change limit. If the temperature difference is less than the predetermined temperature change limit, an estimate of accumulated particulate matter in the after-treatment component is calculated using a primary soot accumulation model. If the temperature difference is greater than the predetermined temperature change limit, an estimate of accumulated particulate matter in the after-treatment component is calculated using a secondary soot accumulation model. The estimate of accumulated particulate matter in the after-treatment component is compared to a predetermined threshold associated with the after-treatment component.