PMC model is a kind of system-level fault model based on test.To counter the weakness in traditional diagnosis algorithm

we have set up a framework of equation diagnosis algorithm for PMC model in 2003.The chief works in this paper are as follows:(1)The past theorem is further replenished and complemented;(2)A simple and convenient method for directly getting absolute fault base is given;(3)By introducing the concept of direct sum

more dimensions PMC fault models are separated into less dimensions models to diagnosis;(4)Equation diagnosis algorithm’s applications are illustrated by examples.