In this paper, we propose a weighting factor (WF) estimation scheme for phase-control based peak power reduction (PPR) of turbo-coded OFDM signal. In this PPR scheme, the peak power of OFDM signal is reduced by adjusting the phase of parity-carriers by multiplying WFs. At the receiver, WFs are estimated at turbo-decoder without using any side-information. The proposed WF estimation scheme is based on an iterative decoding of turbo-code, i.e. the turbo decoder provides not only error correction capability but also WF estimation function. When a turbo-code of the constraint length of K = 4 and the code rate of R = 1/2 is employed, PAPR of OFDM signal at the CCDF of 10-4 can be reduced by about 2.1dB by applying the PPR scheme. The proposed scheme achieves good BER performance comparable to the case of perfect WF estimation in attenuated 12-path Rayleigh fading condition. The degradation in BER performance is about 1.0dB, 0.4dB and 0.2dB at BER=10-4 for turbo-coded OFDM signals using QPSK, 16QAM and 64QAM, respectively.