The model containing coupled subsystems (MCCS) is introduced in [1] to describe systems encountered in nature, engineering, etc. The model is described by a system of ordinary differential equations (ODE), where subsystems are autonomous ODEs. The coupling between subsystems is characterized by a numeric parameter ε, the subsystems becoming independent as ε = 0. The N-planet problem serves as an example of the MCCS with single-leveled subsystems. In this paper we consider the MCCS that contains three subsystems at a single level. The subsystems are supposed to operate in the ordinary mode. The problem existence of oscillations is solved.