Yep, the shop manuals for Toyotas are almost idiot's guides. They
give specific tests, but no clue as to how the system operates. I
think Toyota wants you to pay for a course to find that information
out. I've seen pieces of Toyota training publications and they are
more generic, but do define how various systems function.

The Chevrolet guides I've used (2000) has a lot more design type info
in their manual. A similar year Toyota is just different,

PTC thermisters are regularly used for battery pack protection and
solenoid protection. They are way more reliable for this application.