My 1998 GMC Sierra 2500 4x4 with a 6.5 turbo diesel started giving me problems yesterday when I got off the highway. After stopping the truck wouldn't respond to a throttle command, partial or WOT, didn't seem to matter. Only seems to do this after coming down to a stop from highway speeds, city driving everything is normal.

I pulled 2 codes
p0251 and p0236, these may be old history codes, as the CEL hasn't been on in awhile. Also there is no misfire being felt.

Any help would be appreciatted.

Jason

Welcome to the site. Delete the code and see if it shows up.

P0236 is usually the turbo wastegate solenoid or the vacuum line. You have to make sure there is no leak on the vacuum line. You can change the wastegate solenoid or install at TurboMaster (mechanical) wastegate.

P0251 is an IP code. Have you put like Diesel fuel additive and/or 2-stroke oil? If not, may want to start. In general, this code usually point to a new IP. Let's try to see if there is any other easier things to fix first. Is your LP working, etc. Where is your PMD located?

My best suggestion is to DO the diagnostic checklist so you don't have to answer all the information question one at a time.