Isx15 randomly shutting down

[redtop23]

Hey everyone, first time posting here. Appreciate the help in advance.

I'v got a 2012 pete 587. Cummins isx15 CM2250. Truck has about 1.1 million miles. Original engine. No overhaul. Does have a def mandate.. since about 500k miles ago. Very well taken care of.

Here's the issue, engine dies randomly but only at idle especially after running at cruising speed, then coming to a stop and after a few seconds it cuts off...sometimes. There's times I can go for a whole week and it won't happen, it is getting worse now to where it's almost impossible to drive. Basically cuts off almost every time rpm's drop to idle. Sometimes it doesn't full quit, it will drop rpm almost dying and idles back up. Anytime I am able to give it full gas before it quits I can keep it running.

Here's the fun part, No check engine light! No codes whatsoever. Iv seen the couple threads on here with similar issues and tried the few things suggested. Tapped on the ECM..did nothing. Checked grounds and the few places that Rawze mentioned where wires can rub through.. nothing unusual. Since the truck dies only during idle I'm suspecting a fuel issue? Injector leak? I'v replaced the high pressure fuel relief valve that sits on the end of the fuel rail, retorqued the injector feed tube nuts 57 ft lb "none were lose", and retorqued the high pressure fuel lines of course. All were fine as well. Do I need to do a injector leak down test next?