Battery ran dead now speedometer doesn't work

Hey guys. I wrecked my 99 GMC yesterday. In the midst of all of us being around the crash site, my mother's base model 03 Neon had it's hazards on for a while (an hour or so? probably longer) ran the battery down. We had it jumped off and then we noticed the the speedometer wouldn't work anymore. (It would come up a slight bit, recognizing that there is power to the stepper motor but not going up in vehicle speed)

Any ideas as to where to look?

However, there have been DTC's coming on P0700 "Trans control system malfunction", and P562 "System low voltage" but I read it up that both codes are somewhat related.

P1604 has been coming on also but we know about this already but we haven't taken care of it, but it's not harming the car any.

Thanks in advance.