We present a novel maximum-likelihood (ML) joint frame synchronization and carrier phase ambiguity resolution algorithm for coded systems that exploits the code properties by accepting soft information from the MAP decoder. Simulation results are presented for turbo codes, and are compared to performance results of a conventional algorithm that does not use the code properties. We show that codeaided frame synchronization and phase ambiguity resolution is required for turbo codes, in order to avoid either significant BER degradations or the need for very long pilot sequences. KEY WORDS frame synchronization, phase ambiguity resolution, turbo coding