My son's truck will be driving fine and then all of a sudden the accelerator will stop responding. My son says that the dash will go haywire for a second just as it starts. It idles fine afterward but you have to wait before being able to get any response from the pedal. Then it runs fine for a few days/weeks before doing it again. I've driven it without being able to recreate the issue and no codes show up other than the two codes caused by a exhaust leak. Any help would be appreciated.

Define "haywire"? It sounds like it's going limp, but it could also be a power issue. The ECM relays on almost all years of the R51 are known to cause issues, and sometimes they'll cause low voltage dropout of the ECM. Since that basically puts the ECM to sleep, there are generally no telltale codes.

He says all the gauges go to zero and the dash lights, including the hazard lights which he turns on, go off and the truck idles. You have to coast to a stop and switch the truck off for about 10 mins before it will respond to the accelerator. When you turn the truck off the hazard lights come on. If you start the truck before its ready, the lights and all work fine and it idles but if you push the accelerator it dies. I was told by someone that it could be a faulty cam/crankshaft position sensor. We recently had the timing chain replaced, could it be just enough out of time that it seems to run fine but hits just right now and then to cause a problem?

No, mechanical out-of-time conditions don't come and go. The fact that all the gauges zero out implies either the ECM has stopped sending information to the cluster or there's no power to either one, and given the behavior of the lights, I'd lean toward a complete power disruption. Go over the battery cables thoroughly (use voltage drop and not visual inspection), check the ignition switch for high resistance or mechanical looseness, and make sure all the grounds you can get at are actually grounding. One other thing to check is the battery card, make sure it isn't fractured at the bend and intermittently losing contact with the battery.

Howdy! How's the Pathfinder now? That also sounds like an ECM or electrical issue to me. It would dangerous if that happens on a busy highway. Hope you'll be able to fix that soon.