grounding issue?

[mmccall1]

I'm having trouble finding the engine grounding strap(s) on my 2015 f13.

Symptoms - car failed on highway with battery discharge warning
after replacing the battery, no start/no crank
car cranks and starts when using jump battery from front pos/neg terminals
voltmeter reads 14.6 on front points, but 12.6 declining as battery drains in the trunk. - alternator appears to be working but not reaching the battery compartment.
receive a voltage reading across engine mount to negative front post

all this has led me to believing its a grounding issue.

problem: the only ground straps I've been able to locate are on the tailpipes at the rear of the car

Any ideas on the issue or knowledge of where the engine grounds are?