METHODS FOR VEHICLE EMISSIONS CONTROL

Methods are provided for emissions control of a vehicle. In one example, a method for an engine may include, responsive to a plurality of diagnostic entry conditions being met, indicating degradation of a hydrocarbon trap based on an NHamount in an exhaust gas. In some examples, the NHamount may be determined based on one or more NOsensor outputs. In some examples, the plurality of diagnostic entry conditions may include the engine having been in operation over an initial duration immediately following an engine cold start. Conditions of the exhaust gas following the engine cold start may be opportunistically utilized in determining the NHamount from the one or more NOsensor outputs. In some examples, the exhaust gas may be actively provided at a predetermined air-fuel ratio to meet at least one of the plurality of diagnostic entry conditions.