The generator matrix

 1  0  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
 0  1  1  3 5X+2  6 5X+4  5  0 5X+1  3 5X+2  6  0  X 5X+1 5X+1  5
 0  0 5X  0 5X  X 5X  X 6X 2X  X 6X  0 4X 4X 6X 4X 5X
 0  0  0  X 4X 4X 3X 6X  0 6X  X 6X 5X 5X 4X 5X  0  X

generates a code of length 18 over Z7[X]/(X^2) who´s minimum homogenous weight is 91.

Homogenous weight enumerator: w(x)=1x^0+528x^91+1176x^96+3192x^98+4116x^102+14112x^103+10704x^105+24696x^109+42336x^110+16068x^112+588x^119+132x^126

The gray image is a linear code over GF(7) with n=126, k=6 and d=91.
This code was found by Heurico 1.16 in 1.13 seconds.