Abstract: An apparatus, system, and method are disclosed for estimating ash accumulation. An interpolation module calculates a first particulate accumulation from an interpolation function. An ash feedback module calculates an ash accumulation as an ash feedback function of the first particulate accumulation and a stored first ash accumulation estimate. In one embodiment, an ash feedforward module calculates an added ash estimate. An ash accumulation module may calculate a second ash accumulation estimate as the sum of the ash accumulation and the added ash estimate. A regeneration module may deep clean the filter if the second ash accumulation estimate exceeds an ash threshold. In one embodiment, a soot calculation module calculates a soot accumulation as a second particulate accumulation minus the second ash accumulation estimate.