The Architecture & Supplier Identification Tool (ASIT) is a design support tool enabling generation of system architectures in early design with consideration of supplier identification and evaluation. Several types of uncertainties have been considered in ASIT in order to estimate the overall uncertainty of the architectures. However, the subjective uncertainty caused by expert estimation had not been taken into account. Due to new technology integration and lack of information in early design, expert estimation is commonly used, which is also the case in the ASIT. As a considerable source of uncertainty, the consideration of subjective uncertainty may significantly influence the ASIT results, thus impacting the reliability of ASIT. This paper aims at understanding the sensitivity of the ASIT when subjective uncertainties are taken into account. The type-1 fuzzy sets and the 2-tuple fuzzy linguistic representation are selected to represent subjective uncertainties. A powertrain case study has been used to compare the results and test the sensitivity of ASIT. The comparison shows that the subjective uncertainty does not considerably influence ASIT results, and the ASIT is robust.