The generator matrix

 1  0  0  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1 2a+2 2a  2  1  1  1  1 2a  1  1  1  1  1  2  1  1  1  1  1  0  0  1  1 2a+2 2a 2a+2  0  1  1  1
 0  1  0 2a+2 2a  2  1 3a+2 3a+3 2a+3 2a+1 a+2  a a+1 a+3  3 3a 3a+1  1  1  1  0  1  a 3a+3  1 2a  2 a+3 2a+3 a+2  1 2a+2 2a+1  3 a+1 3a+1  1  0 3a 3a+2  1  1  1  1 a+2  a 3a+2
 0  0  1  1  a 3a+3 3a+1 a+1 a+3 a+2 2a+1 3a+2 2a+2 2a+3 2a  2  3 3a 2a+1 3a a+1  2 3a+3  0 3a+1 3a+2 3a+2 a+3 2a+2  a a+2 a+3 2a+3  1 2a+2  3 3a+2 3a+1  1 2a a+2 3a+2 2a a+3 a+2 2a+1 3a+3 3a+1

generates a code of length 48 over GR(16,4) who´s minimum homogenous weight is 137.

Homogenous weight enumerator: w(x)=1x^0+336x^137+564x^138+180x^139+204x^140+576x^141+228x^142+192x^143+102x^144+300x^145+168x^146+120x^147+81x^148+288x^149+84x^150+48x^151+21x^152+156x^153+300x^154+36x^155+39x^156+72x^157

The gray image is a code over GF(4) with n=192, k=6 and d=137.
This code was found by Heurico 1.16 in 1.99 seconds.