The generator matrix

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

generates a code of length 9 over Z2[X]/(X^2) who´s minimum homogenous weight is 4.

Homogenous weight enumerator: w(x)=1x^0+148x^4+560x^6+1374x^8+1248x^10+644x^12+112x^14+9x^16

The gray image is a linear code over GF(2) with n=18, k=12 and d=4.
As d=4 is an upper bound for linear (18,12,2)-codes, this code is optimal over Z2[X]/(X^2) for dimension 12.
This code was found by Heurico 1.16 in 0.0275 seconds.