my 99 dodge cummins only has first and reverse pulled codes it only had one code 1688 truck want shift out of low gear at any speed or rpm changed output senior and gov pres siol and transducer no help so i pulled the trans thinking it was toast but again wrong its a 48re its at shop shop tech it wasnt bad enough to cause shifting problems is there a way on a diesel to by pass the electronics in trans to make it shift as a test? if so will it damage something else in the truck by doing that? Really need Help

 

Are you sure it's 1688?

P1688 Internal Fuel Injection Pump Controller Failure

You can do a pressure test that will give you something to go on.

http://www.atraonline.com/manuals/se...0/2000_154.pdf

 

well ive had the trans rebuilt still same just low and rev so unpluged trans and tested it it shifted manully from first to third any thoughts on this could lift and injector pump cause this

 

That implies an electronic problem. But, you aren't getting any trans codes..... That's rather odd. I don't think either pump should affect the trans though..... So, question becomes, are you getting power down to the trans?