I have a 2002 dodge ram 1500 6 cylinder. Truck has been having issues with cranking but not starting one day and then the following day or two it will start up without an issue. Errors coming up is p0340 and 1391. Ivd had the computer changed on this vehicle already and it ran well for about a month and then it started to act up again. my son took it to school on Thursday morning and then it wouldn't start by the evening, then today at 500pm, I went to start it and started up with out an issue.

 

Replace the cam position sensor. It's under the distributor cap. Bring your arm with three elbows. It's fun to get to.