Question: how to indicate the desired scene for plot DE

c1 := u1*u2-u1*u3;

c2 := -u1*u2+u2*u3-(1/2)*((u2-u3)*(u1*u2-u1*u3)+(u1)*(-u1*u2+u2*u3)-(u1)*(u1*u3-u2*u3))/(u1);

c3 := u1*u3-u2*u3+(1/2)*((u2-u3)*(u1*u2-u1*u3)+(u1)*(-u1*u2+u2*u3)-(u1)*(u1*u3-u2*u3))/(u1);

c4 := u1;

d1 := subs(u3=u3(t),subs(u2=u2(t),subs(u1=u1(t),c1)));

d2 := subs(u3=u3(t),subs(u2=u2(t),subs(u1=u1(t),c2)));

d3 := subs(u3=u3(t),subs(u2=u2(t),subs(u1=u1(t),c3)));

d4 := subs(u3=u3(t),subs(u2=u2(t),subs(u1=u1(t),c4)));

sys := {Diff(u1(t), t) = d1,

Diff(u2(t), t) = d2,

Diff(u3(t), t) = d3,

y = d4};

sys := {Diff(u1(t), t) = d1,

Diff(u2(t), t) = d2,

Diff(u3(t), t) = d3};

with(DEtools):

DEplot(sys, [u1(t), u2(t), u3(t)], t = 0 .. 15,number = 3, [[u1(0) = 0, u2(0) = 0, u3(0) = 0]]);

Error, (in DEtools/DEplot/WhichPlot) More than two dependent variables - please indicate the desired scene.