A control module for an aftertreatment system that includes a selective catalytic reduction (SCR) catalyst and an oxidation catalyst, comprises a controller configured to be operatively coupled to the aftertreatment system. The controller is configured to determine an actual SCR catalytic conversion efficiency of the SCR catalyst. The controller determines an estimated SCR catalytic conversion efficiency based on a test sulfur concentration selected by the controller. In response to the estimated SCR catalytic conversion efficiency being within a predefined range, the controller sets the test sulfur concentration as a determined sulfur concentration in a fuel provided to the engine. The controller generates a sulfur concentration signal indicating the determined sulfur.