help - b/up fuse keeps blowing
 

My 2006 Azera Limited keeps blowing its backup fuse (10amp) whenever I so much as move an inch in reverse. Moving from P to D (or even past the manual gate) is OK, as long as I don't take my foot off the brake when passing R.

I've so far burned through 4 fuses and still don't know what the problem is.

Here's some history:

The first time this happened yesterday AM, I just replaced the blown b/up fuse with the spare 10amp and the car ran fine the whole day, including several feet of reversing.

The second time this happened was today AM. I ran out of extra fuses, and decided to use the ABS (10amp) fuse instead, to be able to go pick up extra fuses at the local autoparts store. On the drive, I kept seeing check engine and ABS failure messages on the IP, as expected.

After I replaced the 2nd blown fuse, the check engine light came on. I didn't have my code reader with me (it's a funky bluetooth obd reader + android tablet, and i don't always carry the tablet). Had the local gas station look at the codes, and was told of "speed sensor" and a "high-speed controller link" error codes.

Reversed out of the parking spot at the gas station, and the fuse blew again. Twice.

Nothing on the car (other than as described above) has changed in the past several months. I haven't had the car washed for over 6months, but did drive in the rain several weeks ago. There haven't been any other changes at all (I opened the hood up just yesterday after several weeks of not needing to). The car is stock, there haven't been any major modifications (except, I removed an aftermarket nav system and put the stock 6cd radio back, but that was several months ago).

I'm pretty sure there's some sort of electrical fault somewhere, but can't quite figure out what / where.

Please help! I'm not quite sure what to look for next. Thanks!