Ok, let me just get this out of the way, it was dark, I was in a rush, I was doing a jump start, and I was an idiot and I crossed the positive and negative on the battery. Yes stupid me. Now I get to fix my mistake....

Battery is dead, and the battery fuse is also blown. 04 Accord EX 6 cylinder with about 225k miles. Clearly, I need to get a new battery fuse. Beyond that, before I buy a new battery, can I just attach jumper cables to another car and see if my accord will go into accessory? I'm concerned that the ECU may be blown or other damage... and if it's a big deal then this car is off to the junkyard. Not that replacing the ECU is too big of a job if I need to do it... but my point is I don't know what could be wrong.

So right now 1. Replace battery fuse (I need to get a new one) 2. Test to see if car will go into accessory 3. Get new battery if does.

Is that a solid plan? Or should I do something else?

 

Good plan with a different battery. Hopefully you can get to accessory mode and the fuse(s) did their job and protected your electronic components.

Once main fuse is replaced and battery jumpered, use a test light to check the other fuses. You could have blown other fuses downstream of the main battery fuse before it blew.

 

I really lucked out - the battery fuse did its job, blew immediately and protected everything else. So no other consequences. But let this be a warning to anyone else, no matter how rushed you are don't cross polarity on the battery, take an extra 30 seconds to verify before hooking up those cables!