They are to unlock the radio after the battery has been disconnected.

Check your dealer service records. Mine is listed on them.

 

The standard radio for the SE dont need a code. The radio with navigation needs a 4 digit code to unlock each time you disconnect the battery.

 

I have the radio code for my truck but I've never needed it, even when the battery has been disconnected for an extended period.

 

Same as I found. Battery disconnect only required changing AC controller back to F.

Radio R&R supposedly requires code. Suspect when connector taken removed continuity will be lost between pins keeping memory active.

Good idea to get your radio/key codes from a dealer just to have on hand for when the SHTF. Need to do that myself, understand some may provide at no charge and might even do over phone/email if proper documentation sent. Do we have any dealer/members here who will provide that service for free or minimal cost?
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I didn't know we could switch to F. Figured it was British and celsius only. :-)

 

Owner's manual info.
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Hold down the Recirc button (three arrows forming a circle, far right) and then the climate control power button immediately thereafter. The LCD display will show Fahrenheit and Celsius indicators, and then after a couple of more seconds it will show that the change has been completed. Voila!