The generator matrix

 1  1  1  1
 0  X  0  X
 0  0  X a^7*X

generates a code of length 4 over F9[X]/(X^2) who´s minimum homogenous weight is 18.

Homogenous weight enumerator: w(x)=1x^0+48x^18+224x^27+5832x^32+456x^36

The gray image is a linear code over GF(9) with n=36, k=4 and d=18.
This code was found by Heurico 1.16 in 0.000274 seconds.