Ok, I have installed everything (to recap, I am adding a sub to the factory Infinity sound system in my 08 QC truck). The way I did this is to take a PAC SN35 LOC and I tapped into the LF + and - leads directly behind the HU (dark green/yellow and dark green/orange I believe). I ran this into a Y Adapter so that both R and L get a signal to the amp. Since this was just for a sub, I didn't want to cut any more wires than I had to and figured I could still get the same signal from running a Y Adapter off of one speaker. So anyway, the LF speaker leads are tapped into behind the HU into the PAC LOC and the RCAs are run to the amp. The amp is getting power, I ran 8AWG wire correctly, grounded to the chassis and cleaned a nice bare spot of metal, and ran the remote turn on lead from the cigarette lighter. The amp turn-on light lights up, so I know the amp is getting power and properly turning on. So I get everything hooked up and try to listen to the sub and nothing. The gain adjustments on the LOC are set to probably 85% full (I did this because I was going to handle adjusting the gain at the amp level and didn't want to have 2 different gains to deal with). I don't even think my sub is getting any signal because I cranked the bass all the way up and I don't even feel it moving. So basically, doing some trouble shooting, the following are where I think I may be going wrong. I had the battery connected when I plugged the battery and ground wires into the amp, but it still turns on fine so I don't think I shorted anything out. Just giving all details to try and help troubleshoot.
1) The amp is not getting a signal from the LOC for some reason (I bought it new on Amazon, so I don't think the LOC is bad). I think I have a good tap into the speaker leads, what I did was just strip away some wire cover and wrapped the LOC speaker leads around it and put electrical tape around it. This makes me wonder, do I HAVE to utilize both the R and L inputs of the LOC for it to work? Maybe the Y adapter is my problem, the instructions didn't say I had to utilize both, so I thought I would be ok with a Y. Another thought is does the LOC have to be tapped into AFTER the Infinity amp? I tapped in right behind the HU which is obviously before the amp, so maybe it has to be tapped into after the amp?
2) Bad amp/bad sub - I bought the sub off of the internet as well as the amp, so I assume they are brand new (bought from reputable vendors, albeit not authorized licensed dealers) and I doubt they are the issue.
Long story short guys is I really don't know where to go from here because I was REALLY careful and did everything by the book I felt. This isn't my first time installing equipment and I thought this would be a breeze but am at a loss right now. Any help would be appreciated, thanks.