2011 hd 6.0. Rpm fluctuates at 18 to 2000

[JDC]

I just purchased a 2011 gmc 2500hd Denali with 157000 miles on it.  When the rpms are just below 2000 the needle spikes to 2000 and drops back, as if surging.  It downshifts fine.  If you try to gradually accelerate at that point it shudders as if in to low a gear.  I have not tried pulling anything with this truck yet, but wanted to get an idea whether or not I have a serious problem or not.  

 

I took it it to a dealer to have a diagnostics ran on it and the tech couldn’t get power to the tester, so before I tackle that issue I wanted to see if I had a major issue.  According to some of these forums this looks to be a issue on a lot of newer trucks.

 

any experience with this issue would help.  

 

Thanks

[Mikebtte]

Sounds like it could be an issue in communication to throttle control. Throttle positions sensors wear out from time to time and can cause shifting/ throttle issues.

Turn the key on and engine off, remove the intake tube at the throttle body. Watch the throttle blade while someone slowly pushes and releases the throttle peddle. If the throttle blade is dirty or the sensors are failing you will see a lot of jumping. It should have nice smooth operation. Maybe at around the 2000K % it sticks. 2K is kind of a sweet spot for cruising so if it was worn out it would be in that area.

Other than that you need a Tech II for any other diagnostics. Not much you can do without a tech II on this newer stuff.

Edited November 18, 2019 by Mikebtte