Could be a number of problems. First check the fuses (inside and outside the car), then inspect and check the tension on the alternator belt to make sure is tight.
If that doesn't seem to work unplug the battery for 15 minutes or do the ECU reboot trick and see if it comes back.
If it does, get a Code reader to pull the code. Come back and post it. Depending on the code it could be something wrong with your IAT sensor or PCM.