The generator matrix

 1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  X  X  X  0  0  0  1  1  1  1  X  0  X  0  X  X  0  1  1  1  X  1  X  X  X  X  0  0  0
 0  X  0  X  0  0  X  X  0  0  X  X  0  0  X  X  0  X  X  X  X  0  0  0  X  X  0  0  X  X  X  0  X  0  0  X  0  X  0  X  X  0  X  X  0
 0  0  X  X  0  X  X  0  0  X  X  0  0  X  X  0  X  X  0  0  X  X  0  X  X  0  X  X  X  X  0  0  0  0  X  X  0  0  X  X  0  0  0  X  X

generates a code of length 45 over Z2[X]/(X^2) who´s minimum homogenous weight is 48.

Homogenous weight enumerator: w(x)=1x^0+15x^48

The gray image is a linear code over GF(2) with n=90, k=4 and d=48.
As d=48 is an upper bound for linear (90,4,2)-codes, this code is optimal over Z2[X]/(X^2) for dimension 4.
This code was found by Heurico 1.16 in 0.0152 seconds.