Power loss?

2008 GMC SIERRA
70,000 MILES
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SLYAU
I have the truck listed above at half throttle, my truck moves like a turtle. I've notice on my dash PRD321 usually has a line indicator under the P when I'm in park and moves as i switch gears. So, when that line shows up truck drives perfectly normal and when it disappears truck really struggles power wise.
Jul 28, 2025 at 3:35 PM
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STRAILER
  • ✓ASE Certified Mechanic
  • 54,497 POSTS
  • ASE Certified Mechanic
Good observation, it sounds like the transmission is going into limp mode, it could be bad fluid pressure control solenoid. Let run the codes to see which codes are stored, these tow guides can help.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

and this guide goes over reasons it can be limp mode.

https://www.2carpros.com/articles/reduced-power-limp-mode

Please go over these guides and get back to us.
Jul 28, 2025 at 5:50 PM
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