Was driving just shifted into 3rd and then truck jumped like the tranny poped out of gear and then nothing. truck restarts but runs rough and only at a idle get code 1688 and 1689. If the tranny went would it derate the motor?

 

Sounds like you just had you injection pump (the vp 44) die. those codes are non communication between ECM and injection pump.

What's your fuel pressure reading? I am willing to bet It's in the 4psi range. Very common for the 24v motors. You will also need a lift pump if that is the case.

In the last month or so has the truck felt sluggish? Like a lite down on power most noticeable in the higher rpm range?

I have a feeling this has more to do with the motor than the Nv5600. Is 3rd gear totally missing? Like you put it into 3rd and there is no gear? If so that is another issue all on it's own. That is a tranny rebuild too.

 

Here is some more info for you. Was the only thread I found that has both codes. Either way the 1688 code is NOT good. It pretty much is the death code of the injection pump. A very common failure for 24vs.

Sorry.

http://www.dieselram.com/showthread.php?t=160367

 

Have a good lift pump on behind the facory pump, but don't know if the factory pump is messing things up. I have a injection pump on a 2001 truck every thing I found says it will work but don't know. Broke down in MN and pump is in AR so I want to be sort on sure before I drive that far to get it.

 

Might I suggest www.turbodieselregister.com for this one due to the specifcninfo you need confirmation on.

The site is populated by many Cummins engineers and techs. they should be able to get you back up or exact info very quickly.