This paper assesses and reveals the efficiency of an online diagnosis technique over internal combustion engine for quality tests at the end of the assembly-line based on visual dot patterns of vibration signals. The validation of the other traditional methods will be realised using the visual dot patterns method combined with a matching system. Experiments were carry out in order to evaluate the system for fault diagnosis and monitoring under 5 different types of faults conditions: one inverted piston, one connected rod without half-bush, one discharge equalizer out of housing, counter rotating masses with a phase lag of 180 degrees, one tight oil pump screw.