Dipole-phonon quantum logic (DPQL) offers novel approaches for state preparation, measurement, and control of quantum information in molecular ion qubits. Here we report the first experimental demonstration of DPQL as a spectroscopic tool using the shared motional mode of a CaO⁺-Ca⁺ ion chain to measure the frequency splitting of the ground Ω-doublet of CaO⁺. By comparing the dipole-phonon signal across three trap-frequency ramp ranges, we determine the splitting to be ωₘₒₗ=2π×454±1 kHz and place a lower bound on the effective dipole-phonon coupling. The rate of observation is limited by the low thermal population in the molecular ground rotational state.