DIAGNOSTIC SYSTEM IN AN ENGINE MANAGEMENT SYSTEM

A diagnostic system in an engine management system is provided for generating a diagnostic trouble code (DTC) to indicate the operational status of a component or a sub-system. The diagnostic system includes a diagnostic function module (DF module) for each DTC or a group of related DTCs associated with a component or sub-system. The DF module includes means for executing an evaluation routine to evaluate a component/sub-system to which the DTC of the specific DF module relates, and a dynamic scheduler for determining which DF module may be allowed to execute an evaluation routine at a particular time. Each DF module includes means for producing a ranking value dependent on the operating status of the component or sub-system being evaluated, a ranking value being generated each time an evaluation routine is performed; means for processing and storing statistical results of the ranking values obtained over a number of evaluation routines; means for evaluating the statistical results to produce evaluated data in the form of either an evaluated no-fault signal or an evaluated fault signal, and means for establishing the priority of the associated evaluation routine, and means for transmitting the evaluated signals to the dynamic scheduler.