a method of determining whether a cylinder in an engine system comprising a plurality of cylinders is ready for injection / ignition , the method comprising : monitoring the in - cylinder pressure of each of the plurality of cylinders within the engine system ; determining a pressure related parameter for each cylinder within the engine system ; wherein , in the event that the pressure related parameter in a given cylinder exceeds a first threshold , the method further comprises performing a diagnostic test in order to determine whether the given cylinder is ready for injection / ignition .