Getting 33, 34, and 78 codes
 

I have a 94 1500 with a 6.5 turbo. It starts and runs, but will die and not start for 10 or 15 minutes. Some days it runs fine. Have replaced all GP's and need a turbo bypass actuator. What else can i check?

Where is your PMD located and how old is it ? and have you replaced the CPS????and if you have replaced the CPS did you use a AC/DELCO???the turbo bypass will not cause the problems you are having and is that truck a 1/2 ton vin code S?????????????

please explain PMD and CPS. Don't have a manual for this truck. and yes it's a vin code S.

PMD=Pump Module Driver this is the unit that electonicaly controls fuel to the IP (injection Pump) and the CPS=Crank Shaft Sensor codes 33and 34 are EGR codes these will not keep the truck from running as also the waste gate code you are having
copy paste and do these tests in the following link to the best of your ability and the more info we have the better we can help you
Diagnostic Checklist version 2.0 [10-2009] - Diesel Place : Chevrolet and GMC Diesel Truck Forums

OK. have some info. followed the checklist and here are the answers. 2. 94, 3. 148,000, 4. can't find model #, 5. 1500, 6. yes, 7. good, 8. 1 month old. 9. on pump, part#34583. 11. intermittent. A. yes. 12. yes. A. 33,34,78. 13. cleaned. 14. 1 year old. A. no. 15. cleaned. 16 and 16A. yes. 18. no. 19. 500 to 600. 20. yes. A. down the road. B. no. 21. clear. 23. new. 24. no. 25. no. 26. yes. 27. no. 28. all new AC_DELCO. 29. no. 30. no. 31. pass. 32. #2. 33. no. 34. no. 35. no. 36. unknown.

I would look into replacing the CPS and if you do get a AC/DELCO or a NAPA brand CPS do not try any other brand because you want to save a few dollars as these are inferior and in the end the hassel and time it will take to change it Twice will cost you more in the long run IMO

Did a little research and found a test for CPS. Passed the test fine. Engine still has the top plastic cover on it. Will that cause excess heat on the PMD and is it better to take it off or move the PMD to a different location after replacing?

The cover will hold access heat IMO your better off with out it.If you don't relocate your PMD you will be buying another one your better off biting the bullet and getting relocate kit with new PMD and be done with it.

OK. Thanks all for the help. will relocate new PMD down to bumper and see if that fixes the problem. hopefully less problems from here.

Hopefully that will take care of you but even if it don't it needs to be done sooner or later.