I have a 98 GMC 6.5L turbo deisel. The truck run great, but I keep getting the 0236 turbo code when I run it hard. This happen pulling a load and empty. I have noticed some black smoke that isn't normal from this truck on normal driving . I have friends :help: hat have added proformance part that produce black smoke . I have made no mods to this truck. Should the waste gate vacume servo have 0 vac at 750 RPM and jumps to 20 pound at 2500 RPM is this normal. Any HELP would be great.
Thanks MRG120............

Welcome aboard. Click below for FAQ's, & welcome new member. That will reveal the secrets to how we get it done 'round here. One thing is add your truck to your signature line.... 'cause I'll forget what you have in about 2 posts. ;)

Turbo thread chit chats about everything you wanted to know about your turbo. Actuator vacuum should not be at 0" but more like 15" of vacuum. You say 20 pounds, or are you saying 20" of vacuum? Lots of common points of failure for turbo issues. Vacuum lines, wastegate solenoid, vacuum pump etc, etc.

I have 0" at idle at when I accelerate it bounces up to 15"o 20". It really jumps around. I am going to go threw the test and check list from the links you gave me . Maybe that will point me in the correct direction.
Thanks for all the information... MRG120

I suspect what you may find is that the vacuum lines are cracked somewhere. As the engine "moves around" when you rev it up, it can open and close the cracks in the leaking hose. Just a thought...