The generator matrix

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

generates a code of length 21 over Z2[X]/(X^4) who´s minimum homogenous weight is 18.

Homogenous weight enumerator: w(x)=1x^0+163x^18+140x^19+354x^20+764x^21+357x^22+100x^23+125x^24+20x^25+23x^26+1x^38

The gray image is a linear code over GF(2) with n=168, k=11 and d=72.
This code was found by Heurico 1.16 in 0.234 seconds.