I have a 2016 GMC Acadia. I replaced the radio with a OEM Nav radio. When I turn the key the screen says "locked" Online mentions pushing buttons 1 and 3 and so on except I don't have those buttons.

If your 2005 Cadillac STS is displaying "TheftLock" on the navigation and radio screen after replacing the battery, it means that the anti-theft system has been activated. Here are the steps you can take to unlock the system:
1. Turn the ignition key to the "On" position. Don't start the car, just turn the key to "On" position.
2. Wait for the "TheftLock" message to disappear from the navigation and radio screen. This may take up to 10 minutes.
3. Press and hold the "1" and "4" buttons on the radio simultaneously for several seconds until "000" appears on the screen.
4. Use the "TUNE" knob to enter the code that was provided with the vehicle's owner's manual. If you don't have the code, you will need to contact a Cadillac dealership or a certified mechanic to retrieve it for you.
5. Once you entered the correct code, press the "AM/FM" button to unlock the radio and navigation system.

If all doesn't work, it's time to contact a Cadillac dealership or a certified mechanic to help you sort it out.

Here is your 478 page Owner's Manual as a PDF file.
https://cdn.dealereprocess.org/cdn/servicemanuals/gmc/2011-acadia.pdf

Expensive to buy as a paper version!

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GMC Acadia Owner's Manual PDF [2007-2022]

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The radio has to be reprogrammed at the dealer if it is locked - the screen will say - locked. Your problem is likely a failed radio if only one side doesn't work.

The radio and BCM needs read for codes. No reason for the radio not to work after a FOB program. Just a guess, but if the battery power was to low, radio is locked out.

Try spraying contact cleaner to your on/off sw., turn the sw. on & off 5 or 6 times, also try spraying the door button sw.

Grab the remote for the garage door you want to program, then pick a button you want to match the door, next is turn key on push button on the truck and then button on the remote, hold both buttons until flashing red light turns green. you can do this with each button and each remote.

{: ) If the radio displays LOC, LOCKED, or CODE, the radio needs to be reprogrammed to your vehicle.

hi i don't know how many miles or time frame this is but this might be helpful
Updated Warranty and Goodwill Exchange Program for Electronic Products - (Feb 25, 2009)
like my car is a 01 grand prix the cat convertor was warranty 8 years they updated to 10 years
give the dealer a call
good luck

Installing the DVD Map Disc Your dealer/retailer may have installed the map DVD. If the map DVD was not installed, do the following to load it:
Read the following steps completely.

1. Turn the ignition on. The vehicle must be in P (Park) to perform this operation.
2. Press (power) to turn the navigation system on.
3. Press the NAV hard key.
4. Touch the Insert Map Disc screen button. The screen opens to access the map DVD slot.
5. Load the map DVD partway into the slot. The system pulls it in. The screen cannot be closed until a double beep is heard.
   Notice: Pressing directly on the navigation screen may cause damage. Repairs would not be covered by the vehicle's warranty. Do not press directly on the navigation screen.
   
6. To close the screen, slightly push up on the two outer corners until the screen is in position. Then push the screen in by pushing on the four outer corners until a click is heard.
7. Set the search area. See "Setting the Search Area" earlier in this section.

Ejecting the DVD Map Disc The navigation portion of the system cannot be used if the DVD map disc is not loaded.

1. Press the MENU key to enter the Menu options, then press the MENU key repeatedly until Nav is selected or touch the Nav screen button.
2. Touch the Map Database Information screen button.
3. Touch the Eject Map Disc screen button. The screen tilts, exposing the map DVD slot.
4. Press the eject button, located next to the DVD map disc slot, and the disc ejects. Pull the disc out. The screen cannot be closed until a double beep is heard.
   Notice: Pressing directly on the navigation screen may cause damage. Repairs would not be covered by the vehicle's warranty. Do not press directly on the navigation screen.
   
5. To close the screen, slightly push up on the two outer corners until the screen is in position. Then push the screen in by pushing on the four outer corners until a click is heard.