So I installed a aftermarket stereo head unit into my 2007 Scion tC I felt like I did everything properly but now my ABS light
and Brake light came on and my speedometer won't work and to top it off all of a sudden my battery is completely dead.

What do I need to do?

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Was the battery ok before you installed the stereo? If so, it might be a good idea to test your alternator. Auto Zone will test it for free.