This is the second time that I've had LOC on my radio, am I able to use the same unlock code as the first time?

Step 1: Look at your radio. Check and see if the code "RDS" is written on the face of the radio. If "RDS" is present, contact a GM dealership to have your radio unlocked by them.
Step 2: Check for the identification code. Press buttons 2 and 3 for 8-10 seconds. If a code does not appear on the display, you won't be able to unlock your radio in this manner.
[If that doesn't work vvv]
In order to obtain your radio unlock code, you need to find your radio's serial number. You can get the radio serial number directly from your radio.
Step 1: Turn on the ignition. Turn the key to "accessory" mode or "on" mode.
Step 2: Turn on the radio. Press the power button to turn on the radio.
If your radio displays any functions such as playing a CD, cassette, or a radio station, your radio is not locked. If no sound is heard, you may need to replace your radio unit.
If your radio is locked, "LOC" is displayed on the screen.
If "INOP" is displayed, keep your ignition on for 60 minutes with "INOP" on the display. After the hour is up, it should change to "LOC." After this you can proceed with the next step.
Step 3: Write down the code. Press buttons 2 and 3 at the same time and hold for 8-10 seconds. Write down the three-digit code that is displayed.
Step 4: Note down the code. Immediately press the AM/FM button. Another three-digit code is displayed. Write it down as well.
This is your six-digit radio serial number.

Now that you have your radio's serial number, you can obtain the radio unlock code from General Motors. Be ready with a pen and paper to write down your radio unlock code.
Step 1: Contact the GM radio hotline. From any landline or cell phone, call the toll-free GM Radio hotline at 1(800) 537-5140.
Step 2: Enter the code. When it requests a code, enter "106010" on the keypad, followed by the pound (#) sign.
Step 3: Enter the radio serial number. You will be prompted to enter the radio serial number you have just obtained.
At the prompt, enter the number followed by the pound sign.
Step 4: Write down the radio unlock code. The prompt will read out your four-digit radio unlock code. Write it down precisely.

Now that you've obtained your Chevrolet radio unlock code, you need to enter it into your radio.
Step 1: Switch on the radio. Turn your ignition on and press the radio power button. Your radio will display "LOC."
Step 2: Enter the first two digits of the radio unlock code. Press the hour button on the radio to enter the first two numbers of your radio unlock code.
Continue pressing the button repeatedly until the first two digits of the radio unlock code are displayed.
Step 3: Enter the last two digits of the unlock code. Press the minute button until the last two numbers of the radio unlock code are displayed.
Repeatedly press until they match the two digits you need.
Step 4: Confirm the code. When the code matches, press the AM/FM button. "SEC" will display on the radio, indicating a successful attempt to enter your radio code.
If you enter the code incorrectly eight times, the display will switch from "LOC" to "INOP." You'll need to leave the ignition on for an hour as described in Part 2 before you can retry.
Write the radio unlock code in a safe place such as in your owner's manual for future use.
Most car dealers will charge you a lot of money just to get the code for you. If you follow the right steps, you can get the code for free and be able to start listening to the radio again in just a few minutes!
How to Unlock Chevrolet Theftlock Radio

dealer with vin or vehicle and proof of ownership

Requirements
The theft lock radio must be in "LOC" mode.

Procedure:
1. Turn the ignition ON (The radio should display "LOC")
2. Hold down the Radio Presets 2 and 3 buttons for six seconds
3. The radio display changes from LOC to a three-digit number. Write this number down. You now have fifteen seconds to complete the next step.
4. Press the AM/FM button
5. The radio display changes to another three-digit number. Write this number to the right of the first one.
6. You now have a six-digit number, the first three digits are from STEP 03 and the last three digits are form STEP 05
7. Call 1-800-537-5140
8. Press 1 then # (pound). You'll hear "Invalid Code, try again"
9. Press 139010 or 106010 or 206010 or 202107 then # (pound). You will be asked to enter your four or six digit code followed by *
10. Enter the number from STEP 6 then *
11. Listen to the four-digit number and write it down. It will be repeated twice
12. Turn the ignition ON (The radio displays LOC)
13. Use the MN and HR buttons to enter the code from STEP 11
14. Press the AM/FM button. The radio display changes to "SEC". Your radio is now "un-locked" and usable.


Dealership Codes

• 139010
• 106010
• 206010
• 202107

Troubleshooting
If you fail to enter the correct code eight times, the radio goes into INOP mode. You have to wait an hour with the ignnition on before the radio returns to LOC mode.

Procedure:
1. Turn the ignition ON (The radio should display "LOC")
2. Hold down the Radio Presets 2 and 3 buttons for six seconds
3. The radio display changes from LOC to a three-digit number. Write this number down. You now have fifteen seconds to complete the next step.
4. Press the AM/FM button
5. The radio display changes to another three-digit number. Write this number to the right of the first one.
6. You now have a six-digit number, the first three digits are from STEP 03 and the last three digits are form STEP 05
7. Call 1-800-537-5140
8. Press 1 then # (pound). You'll hear "Invalid Code, try again"
9. Press 139010 or 106010 or 206010 or 202107 then # (pound). You will be asked to enter your four or six digit code followed by *
10. Enter the number from STEP 6 then *
11. Listen to the four-digit number and write it down. It will be repeated twice
12. Turn the ignition ON (The radio displays LOC)
13. Use the MN and HR buttons to enter the code from STEP 11
14. Press the AM/FM button. The radio display changes to "SEC". Your radio is now "un-locked" and usable.

Dealership Codes•139010
•106010
•206010
•202107
Troubleshooting
If you fail to enter the correct code eight times, the radio goes into INOP mode. You have to wait an hour with the ignnition on before the radio returns to LOC mode.

http://www.impalaforums.com/chevy-impala-8th-gen-discussion/270328-how-to-reset-gm-theft-lock-radios.html

Taken from:
http://autoforumz.com/Pontiac-Help-u...pict40505.html

GM DELCO THEFTLOCK RADIO UNLOCK CODE:
1. Press and hold presets 2 and 3 for about 5 to 10 seconds until you
get 3 digits on your display. This is the first 3 of 6 digits you will
need, so write 'em down.
2. After doing step one and writing down the code, immediately press
the
AM/FM button to get the last 3 of the 6 numbers you'll need, and write
'em down. (if you wait too long between steps 1 and 2 and the LOC code
displays again, just start over).
3. Call this number, it's a prerecorded message, so don't worry about
having to talk to anyone...1-800-537-5140. The voice will ask if
you're
calling for Chevy, Pontiac, Cadillac, etc... When you here him tell
you
to press "2" for Pontiac, press 206010 and hit the # key. He'll ask
you
for the 6 digit code that you've written down. Enter that and press
the
* key. He will then give you a code, and the option to get additional
4
digit codes, but one should be sufficient.
4. Follow the normal procedure in your owners manual for unlocking the
radio with your new code...press the hour set button on your radio
until
you get the first two numbers of the code, then press the minute set
button until you've entered the last two numbers. Immediately press
the
AM/FM button once the correct code is entered and the code SEC or
"secured" will be displayed on the display screen. Now, just turn the
radio on, and your ready to roll.
There is an additional step you can take to remove all codes from the
radio and start from scratch by entering your own personalized 4 digit
code so that it won't get you in a pickle again! Just repeat step 4
and
you should get a display screen that reads ---. This means the code is
out, and you can now program your own code. Of course, once you
receive
the 4 digit code from the GM recorded message, just keep it in a safe
place, because you can use that same code again and again should you
have any more problems with it in the future. Good luck, and yes, it
does work.
If this doesn't work, you'll have to physically take the truck to a GM dealership, or purchase a new radio.

The following instructions will allow you to reset any GM (General Motors), Cadillac, Oldsmobile, Buick, Pontiac theft lock radio.

Requirements: the theft lock radio must be in "LOC" mode.

Procedure:
1. Turn the ignition ON (The radio should display "LOC")
2. Hold down the Radio Presets 2 and 3 buttons for six seconds
3. The radio display changes from LOC to a three-digit number. Write this number down. You now have fifteen seconds to complete the next step.
4. Press the AM/FM button
5. The radio display changes to another three-digit number. Write this number to the right of the first one.
6. You now have a six-digit number, the first three digits are from STEP 03 and the last three digits are form STEP 05
7. Call 1-800-537-5140
8. Press 1 then # (pound). You'll hear "Invalid Code, try again"
9. Press 139010 or 106010 or 206010 or 202107 then # (pound). You will be asked to enter your four or six digit code followed by *
10. Enter the number from STEP 6 then *
11. Listen to the four-digit number and write it down. It will be repeated twice
12. Turn the ignition ON (The radio displays LOC)
13. Use the MN and HR buttons to enter the code from STEP 11
14. Press the AM/FM button. The radio display changes to "SEC". Your radio is now "un-locked" and usable.

If you fail to enter the correct code eight times, the radio goes into INOP mode. You have to wait an hour with the ignition on before the radio returns to LOC mode.

Hope this helps; keep in touch.

1. Turn the ignition ON (The radio should display "LOC")
2. Hold down the Radio Presets 2 and 3 buttons for six seconds
3. The radio display changes from LOC to a three-digit number. Write this number down. You now have fifteen seconds to complete the next step.
4. Press the AM/FM button
5. The radio display changes to another three-digit number. Write this number to the right of the first one.
6. You now have a six-digit number, the first three digits are from STEP 03 and the last three digits are form STEP 05
7. Call 1-800-537-5140
8. Press 1 then # (pound). You'll hear "Invalid Code, try again"
9. Press 139010 or 106010 or 206010 or 202107 then # (pound). You will be asked to enter your four or six digit code followed by *
10. Enter the number from STEP 6 then *
11. Listen to the four-digit number and write it down. It will be repeated twice
12. Turn the ignition ON (The radio displays LOC)
13. Use the MN and HR buttons to enter the code from STEP 11
14. Press the AM/FM button. The radio display changes to "SEC". Your radio is now "un-locked" and usable.
Dealership Codes

• 139010
• 106010
• 206010
• 202107

Troubleshooting
If you fail to enter the correct code eight times, the radio goes into INOP mode. You have to wait an hour with the ignition on before the radio returns to LOC mode.

Read more: http://wiki.answers.com/Q/Code_to_unlock_radio_for_Chevy_blazer#ixzz26wZKnNnU

How to Reset GM Theft lock Radio's
Article Disclaimer: This article is meant to be used by Delco Radio owners to reset there radios. In no way is it meant to be used for any unethical or unlawful ways.

Purpose
The following instructions will allow you to reset any GM (General Motors), Cadillac, Oldsmobile, Buick, Pontiac theft lock radio.

Requirements
The theft lock radio must be in "LOC" mode.

Procedure:
1. Turn the ignition ON (The radio should display "LOC")
2. Hold down the Radio Presets 2 and 3 buttons for six seconds
3. The radio display changes from LOC to a three-digit number. Write this number down. You now have fifteen seconds to complete the next step.
4. Press the AM/FM button
5. The radio display changes to another three-digit number. Write this number to the right of the first one
6. You now have a six-digit number, the first three digits are from STEP 03 and the last three digits are form STEP 05
7. Call 1-800-537-5140
8. Press 1 then # (pound). You'll hear "Invalid Code, try again"
9. Press 139010 or 106010 or 206010 or 202107 then # (pound). You will be asked to enter your four or six digit code followed by *
10. Enter the number from STEP 6 then *
11. Listen to the four-digit number and write it down. It will be repeated twice
12. Turn the ignition ON (The radio displays LOC)
13. Use the MN and HR buttons to enter the code from STEP 11
14. Press the AM/FM button. The radio display changes to "SEC". Your radio is now "un-locked" and usable.

Dealership Codes
139010
106010
206010
202107

Troubleshooting
If you fail to enter the correct code eight times, the radio goes into INOP mode. You have to wait an hour with the ignition on before the radio returns to LOC mode.

To Read the original article or read similar articles please visit kingbain.com/how-to/unlock-gm-theftlock-radio-s

Good luck (remmeber comment and rated this).

this did not work it says code 139010 is invalid to I cant get past step 8 or 9 my number from step 3 is 702 and step 5 is 706 someone please help Im going crazy

Good Day,

The following procedure will give you a new code that you can use instead of your personal code. Using this new code, you can “unlock” your radio and then “re-lock” it with a new code if you wish. Prerequisites: The radio must be in LOC mode NOT in INOP mode. Let me explain. If you have activated the Theft-Deterrent feature of your radio and loose power, the radio goes into LOC (theftlock) mode. With the ignition on, you must use the MN and HR buttons to enter you personal code in order to unlock it (The instructions are on page 3-27 in your Owner’s manual). If you fail to enter the correct code eight (8) times, the radio goes into INOP mode. You have to wait an hour with the ignition on before the radio returns to LOC mode (go for a long drive somewhere).

Procedure:

01. Turn the ignition ON (The radio displays LOC)

02. Hold down the Radio Presets 2 and 3 buttons for six seconds

03. The radio display changes from LOC to a three-digit number. Write this number down. Don’t take forever, fifteen seconds max before the next step.

04. Press the AM/FM button

05. The radio display changes to another three-digit number. Write this number to the right of the first one.

06. You now have a six-digit number, the first three digits are from STEP 03 and the last three digits are form STEP 05

07. Call 1 800 537 5140 08. Press 1 then # (pound). You’ll hear “Invalid Code, try again”

09. Press 139010 then # (pound). You will be asked to enter your four or six digit code followed by * (start)

10. Enter the number from STEP 6 then * (star)

11. Listen to the four-digit number and write it down. It will be repeated twice

12. Turn the ignition ON (The radio displays LOC)

13. Use the MN and HR buttons to enter the code from STEP 11

14. Press the AM/FM button. The radio display changes to SEC Your radio is now “un-locked” and usable. The Theft-Deterrent feature is STILL active! If you want to disable it, use the instruction on page 3-27 in your Owner’s manual. Use the code from STEP 11 instead of your personal code.

I hope this helps

This came from:
http://answers.yahoo.com/question/index?qid=20070717061922AA7xMG3