2008 Santa Fe radio (with nav) randomly shuts off. Not a fuse issue (replaced). Sometimes won't turn off when key removed.

Google 2008 Hyundai Santa Fe recalls and TSB's at an autoparts site like autozone.com

No recalls that I can find. Any other suggestions? If it's the amp that thing is outrageously expensive (Infinity sound system). Aftermarket radio is under $200. Might be worth it to just replace the bad unit.

I know this is late! but this may help someone else!! I don't know if this will help but I just had a problem with my stereo. I have a 2011 Hyundai Santa Fe and my stereo would not boot up. You may need to update your stereo. I have an Advent stereo/navigation system. I read on a forum: 1.) Press and hold your finger to the middle top portion of the screen of your Advent (if you have this stereo) as you start your vehicle until you see it flash a solid green. You will then see a code prompt. Default coded 1630 and then press enter. You will then see a series of commands. Scroll to Update all. Execute. This forces the Unit to reinstall everything from the memory card. It does take some time. You will see multiple updates. (Do Not interrupt or shut off the Unit until Done!!!) The unit will shut down when done and then restart when the installation is complete. This might take a few minutes, Again do not interrupt!! I am no technician or have any knowledge on how this unit works. This just worked on my unit and I am thankful for Patrick Davis who I give credit for this information. He posted this back on 12/11/16 in one of the forums at www.gm-trucks.com.