The passive localization using multiple sensors is considered for emitter transmitting pulse signals with unknown start transmission time and period. Time of arrival (TOA) of a pulse is estimated at every sensor, and it is difficult for sensors to intercept all pulses during the observation time in practice, as there maybe obstacle on the line of sight or the signal is too weak to be detected, namely, incomplete measurements. In this paper, an algorithm based on a combination of a new second difference of coherent time delays (SDCTD) measurement and traditional time difference of arrival (TDOA) is proposed to improve localization performance in the presence of two kinds of TOA errors, including the independent estimation errors and common errors among multiple sensors. The Cramer-Rao lower bound for the proposed algorithm is derived, and the simulations validate that the performance of the proposed algorithm significantly outperforms existing algorithms, especially in the case of pulse loss.INDEX TERMS Multi-sensor passive localization, incomplete measurements, second difference of coherent time delays, time difference of arrival, Cramer-Rao lower bound.