A control unit 8 and method for controlling reactivation, regeneration or purging of a lean NOx trap (LNT) in an exhaust system 3 of an internal combustion engine 2, e.g. of a vehicle. The control unit has a processor 11 configured to generate a reactivate flag for the LNT, and a memory device 12 having instructions and coupled to the processor. The processor is configured to generate the reactivate flag when it determines that an adsorption capacity and/or efficiency in the LNT is reduced by identifying that the exhaust gas supplied to the LNT is lean, and an LNT temperature is greater than or equal to a predefined LNT temperature threshold. In dependence on the reactivation flag, the processor may generate a reactivation request signal when the exhaust gas temperature is less than or equal to a first reactivation temperature threshold and/or greater than or equal to a second reactivation temperature threshold.
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