The generator matrix

 1  0  0  0  1  1  1 X^2  1  0  1  1 X^3+X^2+X X^2 X^3+X^2+X  1 X^3+X  1 X^3 X^2  1
 0  1  0  0  X X^3+1 X^2+X+1  1 X^2 X^2 X^2+1  X  1  1 X^3 X^2  1 X^2+1  1 X^3+X^2 X^3+X
 0  0  1  0 X+1  1  X X+1 X+1  1 X^3+X^2+1 X^2+X X^3+X^2+X X^2+X+1  1 X+1 X^3+X^2+X+1  0  X  1  X
 0  0  0  1  1 X^2 X+1  1  X  1 X^3+1 X+1 X^3+X^2+X+1 X^2 X^3+X^2+X X^3  1 X^2+X X^3+X X^2+X+1  0
 0  0  0  0 X^2 X^3  0 X^3  0 X^3 X^3+X^2 X^3+X^2 X^3 X^2 X^2 X^3+X^2 X^2 X^3+X^2 X^3+X^2 X^3+X^2 X^2

generates a code of length 21 over Z2[X]/(X^4) who´s minimum homogenous weight is 15.

Homogenous weight enumerator: w(x)=1x^0+90x^15+814x^16+3174x^17+11389x^18+28092x^19+54680x^20+65258x^21+55260x^22+28202x^23+11211x^24+3058x^25+741x^26+112x^27+46x^28+14x^29+2x^30

The gray image is a linear code over GF(2) with n=168, k=18 and d=60.
This code was found by Heurico 1.16 in 114 seconds.