This paper presents a systematic measurement approach for localizing the acoustic leakage of pass-through components and for determining the pass-through effects on sound transmission loss through the front vehicle dash section. The dash section is cut from a current vehicle platform and is installed on the wall of a sound transmission loss suite in which the source side is a reverberant room and the receiver side is a quiet room. The proposed approach is based on the widely-used sound intensity technique. The transmitted point and spatially averaged sound intensities through the dash section are measured with the careful control of noise flank paths and reactive fields. The approach includes sequential steps of measurements on the dash section: (1) bare panel with all holes sealed; (2) with dash insulator installed; (3) with each of four pass-through component groups installed; (4) with all pass-through component groups installed; (5) with instrumental panel installed. The acoustic leakage due to pass-through components in steps 3, 4, and 5 can be identified and ranked by displaying all point intensities into contour maps with respect to steps 1 and 2 in which no pass-through component is installed. The corresponding sound transmission loss is calculated by using the spatially averaged intensities. This approach proves to be an excellent development tool to evaluate existing and potential acoustic treatments for dash insulator and pass-through components in the vehicle front dash section.