I have a 2011 Dodge Ram 3500 with a Cummins 6.7 with an H&S mini maxx tuner, 5 inch turbo back exhaust, s&b intake, and ego unplugged and the plunger removed. Truck has about 112,000 miles on it, 80% highway.
Yesterday morning after sitting over night, my truck wouldn't start.
It started and ran perfectly fine monday, to and from work.
When i tried to start it, it would turn over maybe half a crank then click then do another half crank but not start. I checked my tuner for codes and it had P020A (injector 1 performance) I cleared the code and tried again and had the exact same code pop up.
I've tried jump starting it. I tried unhooking the batteries and letting it sit for an hour, then hooking it back up, and jump starting it. Both batteries test at 12.23 volts as well as at the starter. I tried smacking the starter solenoid with a hammer while my buddy cranked it and still no change. I removed my tune and changed it back to stock and it did the same thing.

I had all my injectors replaced with brand new ones 20,000 miles ago so I sure as hell hope its not an issue with them, but I don't think that would keep it from starting.
I was towing my 35 foot fifth wheel this weekend for about 600 miles, and truck ran perfectly fine before, during, and after.
Any help figuring this out would be appreciated.
Tomorrow after work my buddy is going to try to bump start it with his truck (mines a manual) and if that works I know its the batteries or starter so I'll drive straight to NAPA and have them test it on their machine.

Please let me know if theres anything I missed or should try to get this thing up and running. Its never left me stranded before this.

 

Sounds like a battery or a battery cable. but i see you checked that is the engine locked up?