09 Cadillac CTS 3.6
This damn car is a nightmare on elm Street type shyt, I hate this car so bad
To see if the starter was bad,or if any grounds were corroded or Rusty etc
So I jumped pin#30 with pin#87 starter was supposed to roll over but it didn't nothing happened so I took a test light and tested the pin#30 and didn't light up no power, so I started looking at the 2 thick red power cables on the red cap post the real thick one I checked up and down the cable and I don't see any fusible link on that one ,the other not so thick cable goes to the alternator I checked the cable up and down and I see a black square flat box with the words 200 amp , is that a fusible link? and can that be the cause why pin#30 has no power? at this point any help is appreciated

2009 Cadillac CTX-4 with a 3.6
The rear battery in the trunk died I put another battery in it tried to start it all interior lights brake lights turn signals the radio the AC the moon roof the power windows the door locks power seats etc it all works when you try to put it in the start position it's quiet you don't hear no clicks no nothing I tried to put it in neutral same thing quiet no clicks no nothing I bypassed the starter relay using a jumper wire from pin 30 to pin 87 and nothing starter did not engage I put the key fob in the pocket under the arm rest and still nothing the key fob doesn't lock or unlocks doors or open trunk I'm trying to avoid the shop to get raped ... Has this happened to anybody if so can yuu a point me in the direction to fix the problem id appreciate it