A method of correcting a soot mass estimate in a vehicle exhaust aftertreatment device includes monitoring an exhaust gas pressure drop across a particulate filter included with the vehicle exhaust aftertreatment device. Following the detection of a pressure drop, a controller may determine a soot mass estimate from the monitored pressure drop; determine an ash volume estimate representative of an amount of ash within the particulate filter; determine an ash correction factor from the soot mass estimate and the ash volume estimate; and calculate a corrected soot mass value by multiplying the ash correction factor with the soot mass estimate. If the corrected soot mass value exceeds a threshold, the controller may generate a corresponding particulate filter regeneration request.