VT Commodore security coded head units

Question

When i started my car the other day it didn't turn over the first time, when i started it the next time my radio didnt work, I tryed entering a code but i got it wrong three times, A couple days later i was able to try the codes again and i worked out that if i entered "1111" it would work for about 3 min. Is there any thing that i can do to fix the head unit. it is a second hand car so i dont have the correct code.