Are you using a fuse tap like pictured here? You have to have both fuses in to make it work for both the device you are powering and the circuit you are tapping into.
Too bad you were not local to me as I would gladly help you with this as it probably at best 30 minutes with a multimeter to have it figured out.
At a minimum, you know it is not the module and I would suggest letting the dealer know that you slaved into your JL and it worked. 90% sure it is...
Not trying to dog pile on you but if basic DC electrical theory is not something you can pick up, you are going to be spinning your wheels trying to make heads or tails of this.
I would disregard the switch back lighting in figuring this out as that is a totally separate circuit that obviously...
I have run 5W-30 and even 5W-40 Euro oil with analysis showing no determent. I am not trying to sell you on the practice so do not ask me to justify it.
Plus you never really owned it, the phone company did. Lose or damage it and you basically got interrogated like it was a state secret sold to the Soviets.
I have multiple personal oil analysis that says it is fine and meets spec. Your opinion on Walmart business practices is just noise to the technical discussion. If there is actual test data and not opinionated supposition, I am all ears and willing to learn.
As to Project Farm, I am well aware...
I have used the brand and other German brands like Ravenol also with satisfactory results. You just seem to want to get miffed when the discussion is not a cheerleading section for it and finds a different value in it.
Their oils are fine if you know what your are buying and nothing wrong...