The localization of Electromagnetic Interference (EMI) sources is very important in Electromagnetic Compatibility applications. Recently, a novel localization technique based on the Time Reversal Cavity (TRC) concept was proposed using only one sensor. In this paper, we discuss the concept of TRC and its application to the localization of EMI sources. We investigate the maximum peak field criterion to localize an EMI source in the cavity using one sensor. We show that the maximum peak field criterion in the presence of the cavity can be used to localize an EMI source with high accuracy. The performance of the proposed criterion is evaluated using the finite difference time domain method. Finally, we provide a proof of concept to show the ability of the time reversal concept in the localization of an EMI source in a cavity. Experimental results confirm that the proposed method can be used in practical EMC problems.