Safety of automotive systems is becoming more involved, specially for the case of autonomous vehicles. The ISO 26262 standard offers a systematic approach for designing a safe road vehicle (or subsystems of a car) from design phase through its production. However, providing functional safety (according to ISO 26262) for an existing system is a challenge which needs further effort. This research addresses the problem of applying ISO 26262 to a system which has already been developed using conventional safety methods. We suggest a methodology for the process of systematically applying the ISO 26262 standard to an existing system.