djlightning

I have a slow crank on my 2018 GMC Sierra even with a new battery. The car is under a bumper to bumper warranty so I took it to the dealer. They say that I need to replace both the negative and positive battery cables due to high resistance. They state that the spec for voltage drop is less than 100mV for either cable and their testing showed a drop of 460mV on the negative cable and 260mV on the positive cable. Has anyone seen something like this before? Cables are not covered unde my warranty and parts and labor are $832. Just based on my experiece with IT cables it usually is a termination/corrosion issue and not the cable itself, let alone both cables at the same time. Maybe it is something else too. Regardless I wanted to seek opinions here before I plunk down the cash on the reapair. Thank in advance for any support.