The increasing complexity of embedded calculators in terrestrial vehicles makes more and more complex their qualification for Electromagnetic Compatibility. The cost of test facilities and certified personnel for a normative test in Radiated Immunity (RI) is high and constitutes a bottleneck for Original Equipment Manufacturers (OEM). To solve their problem, OEM need a quick, economical and easy-to-use investigative system. The Near Field Scan Immunity (NFSI) method is quite fitted to be a good investigation tool when used with immunity probe dedicated to investigation at Printed Circuit Board (PCB) level. But, to be able to compare NFSI measurements to RI ones, problems inherent in NFSI measurement as its dependency to probe's position and the non-consideration of the harness resonances seen during the RI measurement must be solved. This paper presents a methodology to predict the RI immunity level of an equipment after layout or component change from a RI measurement performed on original equipment and NFSI measurement performed on both versions.