Bearings are one of the critical components in rotating machinery. Most of the failures in oil-lubricated journal bearings are related with instabilities produced by bearing wear or lubrication system problems, and effect in increased shaft vibration. Therefore, monitoring of the journal bearing condition in the field mainly relies on analysis of accelerometer signals or proximity probe. However, not all motors with journal bearings are equipped with such mechanical sensors due to cost or environmental restrictions. The need of an effective and easy fault diagnosis technique has headed to the increasing use of motor current signature analysis (MCSA). The objective of this paper is to study about different methods to detect faults (outer race fault) in a mechanical system.