Many people don’t know how to unlock a GM radio so they contact the dealer. This requires a service charge that can reach $100. If the GM radio is on LOC mode because you disconnected the battery, or locked it by other means and you don’t have the unlock code, follow these steps to get it unlocked yourself:
Check the manual of the car because most people write the code in the book. If it’s not there grab a piece of paper and a pen. Turn the key in the ignition to on and check if the display shows LOC.
Hold the radio presets 1 and 4 or 2 and 3 (if you don’t have a forth button) pushed down for about 5 to 10 seconds. A 3 digit number should appear on the display. Write it down quickly because the Theftlock system gives you only 15 seconds to move on to the next step.
Immediately press the AM/FM button and hold it until another 3 digits appear. Write them on the piece of paper to the right of the first code. These are the 6 digits you need to unlock the radio. If you waited too long and the LOC code appears again just start over.
The six-digit number is necessary to get a four-digit code that unlocks the radio. Probably a small fee needs to be payed. If you are a good customer you might get it for free. Use a search engine to find websites that offer Theftlock codes, or call a GM dealer. You can also call this number 1-800-537-5140, select you car model and enter the six-digit code.
This is the last step on how to unlock a GM radio and the most important one. After you get the four-digit code, turn on the ignition and press the HOUR set button on the radio until the first two numbers of the code appear. Press the MINUTE button until you get the last two numbers of the four-digit code. Press the AM/FM button immediately after. If the code SEC appears on the display your system is fully functional. Turn the radio on and see if it works.
If you don’t enter the correct code eight times in a row and the INOP mode appears, wait an hour with the ignition on and it will return to LOC.
If you want to remove all codes from the radio and enter your own four-digit code, repeat step 5 and the display should read —-, meaning that the code was erased and you can enter you own code. Keep the code safe in case you will need it again. Now you know how to unlock a GM radio using your own code.