1. A method of determining the cause of an error state for one or more components within an apparatus comprising a plurality of sensors arranged to monitor the operation of components of the apparatus and a control means arranged to receive said information from said plurality of sensors, the method comprising: a) analyzing said sensor information in the form of an error log to ascertain sensor patterns from said sensor information; b) comparing said sensor patterns with detectors, which are predefined patterns, indicative of the condition of said one or more components within the apparatus; and c) classifying said sensor patterns as being indicative of said error state of a component or not based upon a comparison of sensor patterns with said detectors.