Diagnosis device and method using an in-cylinder pressure sensor in an internal combustion engine

A method of diagnosing faults within an engine system (1), the engine system comprising a plurality of cylinders, the method comprising: monitoring (310) the output signal of one or more in-cylinder pressure sensors (3) within the engine system, each of the one or more in-cylinder pressure sensors being associated with a cylinder within the engine system; determining (312) a pressure related parameter for a given cylinder having an associated in-cylinder pressure sensor; and diagnosing (314) the presence of faults within the engine system on the basis of the pressure related parameter.