It started about two weeks ago. I had to jump my car to get home. When I got to my house I went ahead and got a new battery and ended up replacing it. After doing so we noticed the engine was starting to solely depend on the battery. As soon as we pull out the positive cable the engine would die. Suddenly we also noticed the alternator was starting to release smoke and it was getting really hot. The following day we replaced the alternator for a new one. We give it a go again just to find out the volts are reading 12 on the alternator (it should be reading 14). We figure that maybe it may be a fuse that burned out. We get into the fuse box and check all the fuses. A few were burned out and we replaced them in the correct order. After giving it another go we are short of luck. The car is still relying on the battery and the readings are the same. We also notice the battery is getting drained really quickly of course. A mechanic arrives yesterday and after taking a crack at it tells me that the alternator is the one giving me the trouble. He claims because the alternator was remanufactured (even though it claims to have been triple tested) this was what it was causing the trouble. He heads out to get a new alternator and changes it out. All in all I'm thinking "well this is gotta be it". But no. This morning me and my roommate through youtube tutorials did a test that told us that more likely is the PCM. Do you recommend I try something else?
Why in the world did you disconnect the battery with the engine running? When you did that, you put 14 volts through a computer system that uses 5 volts.
You can't condemn the PCM from a test you did at the alternator wiring connector.
Especially on a Jeep (or any Chrysler/Dodge). It's much more likely to be a wiring issue than the PCM.
Anyway, I guess the "youtube test" you performed didn't see a Ground "pulse" being provided by the PCM at the alternator connector.
Let's look at how this thing works.
The way the "charging rate" is controlled by the PCM is by providing a pulse width modulated ground to the alternator's rotor circuit.
It looks like this. The top of the Square Waves are when the computer turns the "Ground ON" to the alternator and the bottom of the Square Waves is when the computer turns "Ground OFF". It's called "Duty Cycle" and it's proportionate to how much the PCM wants the alternator to charge the battery.
I assume that the youtubes you watched showed you how you can test that alternator connector with a cheap test light.
You should perform that same test at the PCM to rule out (or rule in) a wiring issue between the PCM and the alternator.
So here's an example where you wouldn't want to use any 2012 Jeep Liberty PCM pinouts that you find for free on the internet.
Either call the Jeep Service Dept and see if they'll give you a copy of it or pay the $20 for a 1 month subscription to something like AllData DIY.
You don't want to replace the PCM because of a wiring harness issue
You probably burned out the fusible link on the alternator
Never disconnect the battery on a running engine, you may well have done more damage.
https://www.youtube.com/watch?v=0sWO9NrwOC4
