The topic of fault diagnosis in circuit and systems has acquired great concern in the development of research. This paper presents a novel and intelligent model for fault diagnosis in small signal electric and electronic circuits comprising diodes and BJTs. The first step in this process is to analyse the circuit under test by subdividing it into nodes and branches and thereafter applying Kirchoff's law for the currents at each node to generate a matrix capable of providing the direction of all currents in the circuit. The logical inference engine is then applied to the solid results obtained to induce accurately for the source of fault or faults. This technique was applied to different circuits and proven to be successfully in (98%) of the cases at a very fast rate. A hybridization of both PROLOG and C language was used in erecting this system