I am having issues along these same lines. Bought from auction and it would not get out of limp on the way home and was having issues in and out of SLA positions. Gear display in dash was blank - now it wont start.

error codes -

P2300 (CAN Communication Faulty)
P2313 (Shift Lever Position Invalid)
P240C (SLA CAN Message Incorrect)

I have replaced the SLA (used)(problem persists) and checked the RCM for bad soldering or burns (looked spanking new with great soldering).
New Battery. Alternator looks new.
There is an aftermarket radio system that might not have proper grounding.
Have not checked the transmission fluid.

Any more details on that starter bypass?
could this be a grounding issue somewhere?
does a blacked out gear display indicate anything? this seems unique in research.