The spectrum of triatomic molecules with close rovibrational opposite parity levels is sensitive to the P,T-odd effects. This makes them a convenient platform for the experimental search of a new physics. Among the promising candidates, one may distinguish YbOH as a non-radioactive compound with a heavy atom. The energy gap between levels of opposite parity, l-doubling, is of great interest as it determines the electric field strength required for the full polarization of the molecule. Likewise, the influence of the bending and stretching modes on the sensitivities to the P,T-violation requires a thorough investigation since the measurement would be performed on the excited vibrational states. This motivates us to obtain the rovibrational nuclear wavefunctions, taking into account the anharmonicity of the potential. As a result, we get the values of Eeff and Es for the lowest excited vibrational state and determine the l-doubling.