In the terahertz frequency band, utilizing an OTFS-ISAC vehicular networking system with superimposed pilots can achieve high-speed data transmission between vehicles alongside high-precision parameter sensing. First, the OTFS signal modulation model, communication signal model, and sensing signal model are established and analyzed. At the receiver, a new sensing channel model containing angle information is derived. Subsequently, a coarse angle estimation algorithm based on the uniform grid MUSIC method and a fine angle estimation algorithm based on the golden section MUSIC method are proposed. Finally, a maximum likelihood estimation criterion-based algorithm is proposed for estimating the integer and fractional parts of the channel delay and Doppler shift parameters. Simulation results demonstrate that the proposed algorithms can achieve accurate estimation of sensing parameters such as angle, distance, and velocity.