The generator matrix

 1  0  1  1  1  1  1  X  1  1  1 2X  1  1  1  0  1  1  1  X  1  1  1 2X  1  1  1  1  1  1  1  1  1  0  X 2X  1  1  1  1  1  1  1  1  1  1  1  1
 0  1 2X+1  2  X X+1 X+2  1 2X  1 2X+2  1  0 2X+1  2  1  X X+1 X+2  1 2X  1 2X+2  1  0  X 2X+1 X+1 2X  1  2 X+2 2X+2  1  1  1  0  X 2X 2X+1 X+1  1  2 X+2 2X+2  0  X 2X

generates a code of length 48 over Z3[X]/(X^2) who´s minimum homogenous weight is 96.

Homogenous weight enumerator: w(x)=1x^0+72x^96+2x^99+4x^108+2x^117

The gray image is a linear code over GF(3) with n=144, k=4 and d=96.
As d=96 is an upper bound for linear (144,4,3)-codes, this code is optimal over Z3[X]/(X^2) for dimension 4.
This code was found by Heurico 1.16 in 0.0119 seconds.