I have a 2008 and last week the battery light came on but all checked out good as far as testing both batt and alt. Alt was deemed to be intermitt. bad and replaced yesterday.... HOWEVER today my darling other half tried to jump the car and reversed the cables and basically scared the hell out of me. The IG2 fuse blew and that was replaced however it still will NOT even attempt to start. I am trying to figure out where the next step is because I am lost. All the lights on the dash come on and I have power. Any advice welcomed. Also I was trying to locate a wiring diagram online for this year xB with no luck.

 

All the fuses in the engine compartment checked out OK?

Not sure what kind of damage reversing the battery cables can do? Wonder if one of relays is fried in the fuse block?

Sorry, not much help

 

Have a look at the main bus fusible links in the engine fuse box. Most likely you blew one of them.

Here's a video on replacing it on a Corolla so you can see where it is to check it.