The generator matrix

 1  0  1  1  1  1  1  1  1  0  1  1  1  0  1  1  X  1  1  1  1  1  1  1  X  1  1  1  1 aX  1  1  1  1  1  1  1  1  1  1  1  1  1  X  1  1  1  X
 0  1  1  a (a+1)X+a+1  0 (a+1)X+1  a (a+1)X+a+1  1  0  a (a+1)X+1  1 (a+1)X+a+1 X+a  1  X (a+1)X+1 aX+a+1 X+a  X  1 aX+a+1  1  X aX+1 a+1 X+a  1  0  X aX aX+1 aX+1 X+1 aX+a+1 (a+1)X+a+1 X+a+1 aX aX+a+1 X+1 aX+a  X (a+1)X aX+1 a+1  1
 0  0 (a+1)X  0  X  X (a+1)X  X (a+1)X  X  0  0  X  X  0 (a+1)X aX aX  0 (a+1)X aX (a+1)X aX aX (a+1)X  X  X  0  X (a+1)X (a+1)X (a+1)X  0 (a+1)X aX aX  0 (a+1)X aX  0 aX (a+1)X  0  X aX  0 aX  X
 0  0  0  X aX  X aX (a+1)X (a+1)X  0  X (a+1)X  0 aX aX (a+1)X  0  X  0 aX (a+1)X  X  0 aX  0  0 aX (a+1)X  X aX  0 aX (a+1)X (a+1)X  X aX  X  0 (a+1)X aX  0  X  0 aX aX  X (a+1)X (a+1)X

generates a code of length 48 over F4[X,sigma]/(X^2) who´s minimum homogenous weight is 136.

Homogenous weight enumerator: w(x)=1x^0+621x^136+1110x^140+909x^144+753x^148+525x^152+147x^156+18x^160+3x^164+6x^168+3x^172

The gray image is a linear code over GF(4) with n=192, k=6 and d=136.
This code was found by Heurico 1.16 in 0.112 seconds.