  In this paper we investigate the effects that an anomalous acceleration as
that experienced by the Pioneer spacecraft after they passed the 20 AU
threshold would induce on the orbital motions of the Solar System planets
placed at heliocentric distances of 20 AU or larger as Uranus, Neptune and
Pluto. It turns out that such an acceleration, with a magnitude of 8.74\times
10^-10 m s^-2, would affect their orbits with secular and short-period signals
large enough to be detected according to the latest published results by E.V.
Pitjeva, even by considering errors up to 30 times larger than those released.
The absence of such anomalous signatures in the latest data rules out the
possibility that in the region 20-40 AU of the Solar System an anomalous force
field inducing a constant and radial acceleration with those characteristics
affects the motion of the major planets.
