just checked my manual on my 2000 z71.
i have the single disc cd player and it says as follows.
Enter your secert codeas follows, pause no mre then 15 seconds between
1) turn the ignition on, LOC will appear on the display,
2) press MN and 000 will appear on the display,
3)press MN again to make the last two digits agree with your code.
4) press HR to make the first one or two digits agree with your code,
5) press AM/FM after you have confirmed that the code matches the secert
code you have written down,the display will show SEC indicating the
radio is now operable and secure.
if you enter the wrong code eight (8) times INOP will appear on the
display. You will have to wait an hour with the ignition on before you
can try again. When you try again, you will only have three (3) chances
to enter the correct code before INOP appears.
If you lose or forget your code, contact the dealer.
sorry i should of looked this up first before trying to help ya.