Ab initio calculation with the configuration interaction method is used to obtain the potential curves and the diabatic coupling matrix elements for the OH 3+ system. The configuration interaction method reproduce the experimental values of the excitation energies in a good approximation. The radial coupling matrix elements related to the charge transfer reaction have large values at the avoided crossing points and also in the regions of the smaller nuclear distances. The rotational coupling matrix elements have nearly constant values at larger nuclear distances but change abruptly their values at the avoided crossing points.