Everyone knows to disconnect the battery before replacing an alternator...right? Did anyone ever mention what could happen if you forgot? Well I'll tell you. On my 07 IS250, when using a wrench to remove the nut holding the main cable on the alternator, touching it to ground will short out something called the fusible link. I found this out after replacing the alternator and thinking everything was good until I tried to start the car. Half the electronics didn't work including the ODB code reader and the car wouldn't start. So after saving a few days by buying the alternator from my local Autozone, this fuse could only be ordered on-line and cost over $100. And replacing this fusible link is a royal pain that will take a few hours. You can find details of how to do this in another post.
We use this forum to help each other out, so don't make this mistake when replacing your alternator. It will cost you time and money. BTW, this will also happen if you install the battery backwards and connect to the wrong posts.

 

for the heads up