I have an 98 lumina but the radio is locked What is the code to unlock it

Try this: http://www.ehow.com/how_5791873_unlock-gm-radio.html

Take the registration to the dealer, they can look up the code by your vin#

You will have to have the abs computer scanned for codes. You likely have a bad speed sensor.

dealer only can give them codes

If you do not have the code. look in owners manual some times it is written in there or there is a card with code on it. if not you need to go to a volvo dealer and they can get the code for you. You may have to pay them for it.

someone (hopefully you) set the 3 or 4 digit security code on the radio. when power is disconnected, like if someone steals your radio, the radio locks and cannot be used. the code can be from 000 to 1999. the hour and minute buttons are used to enter the numbers. 2000 choices - good luck
to unlock the system:
1 turn on ignition - LOC will appear
2 press MN and '000' will appear
3 press MN again until you see the last 2 digits of the code you want to try
4 press HR until you see the first 1 or 2 digit of the code you want to try
5 press AM FM
6 SEC will appear if you got it right - LOC will show if you got it wrong
good luck

If your lucky the dealer may still have it or the code may be written down at the back pages of your manual. The other place where you can get the code would be www.radio-code.com. before you try any of that, try 0000 to unlock your radio. Good luck and hope this helps. 

if you do not have the code.gm will do it for 40 dollars.

Call Dealer to get code.Then write it down and save.

I've heard of people using Delco Lock Codes (http://www.delcolockcodes.com) to get their radios unlocked. They seems like a legit site from what I've read. Good luck!!