I have a 2001 gmc 6.6 duramax a few months ago when it would get below 50 degrees it would not go into gear when it had set over night , everything moved properly but it would not ingage. So I would put it into park and wait 10-15 minutes with it running put it in gear and it drove with no issues. I checked the transmission fluid and it was perfect. I read the nsbu's go bad and I bought one and it seemed to work but it still has problems every now and again but once it goes into gear it runs drives shiftes just fine and will not usually do it again unless it sits for a while or gets really cold. About a month later it was geting warmer and now it was getting harder to start but once it did start it ran good. So I bought a lift pump again that's what I kept reading about and that seemed to fix it for awhile but now Then i can take a 20 min drive shut it off And run into the store and came back and it will crank but wouldn't start so I opened the hood and checked if I had any leaks and everything looked fine. Waited probably 30-45 minutes and it started up no problem I thought it was a freak thing so I didn't think twice but now it is happening more often and the only trick I could do to fix it was hold the pedal to the floor and it would start and run and drive fine. So I started today and had to run errands and I never shut it off it ran great got on the highway great idled great then when I got back to the shop shut it off I tried to start it back and it would not start and hours later still will not start still cranks but won't start the primer pump is hard but there is no pressure on the fuel rail unless I turn the key on so the lift pump is on. The thing that really puzzles me about all of this is once it starts and goes into gear it runs and drives just fine no problems until I shut it off. The only codes I get are p0845,p0846,p0841,P1713 and the check engine light does not stay on long it will go off with out being cleared. I was told it might be my CPU has gone bad because I had a edge programmer on it. Does anyone have any ideas what might be going on. And I have already replaced the injectors and injection pump about 57,000 miles ago. Any ideas or help appreciated thank!
