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2018 GMC Sierra 2500 Denali HD
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Discussion Starter · #1 ·
Hi I'm new to the diesel community and just bought a 2018 Denali HD Duramax 11 days ago. To the best of my knowledge no one prior to my ownership has done anything to the motor, transmission or exhaust. Yesterday I was driving normally when every light possible came on. 4wd fault, ABS fault, stibilitrack fault, power steering fault etc. Got home and truck would not start back up right away. Waited 30+ min and came back on with a solid check engine light. Today I drove it for maybe 1 hr and went into limp mode with all the dash lights coming on again. Check engine light has been solid the whole time and now 1/2 shifts late as if I was towing and 2/3shifts so hard it jerks the whole truck. Has about 142k and im not sure if I should bring to the dealership I bought it from (2hrs away) or to a local GM dealer. Any insight or help is very helpful. Thank you in advance!
 

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If your truck is still under factory warranty take it to any GM dealer. At a minimum, they should determine what's wrong, read error codes, etc and that should be your lead-in as to your next actions. The symptoms can be from many causes and only testing can determine exactly what needs to be done.
 

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2018 GMC Sierra 2500 Denali HD
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Discussion Starter · #3 ·
If your truck is still under factory warranty take it to any GM dealer. At a minimum, they should determine what's wrong, read error codes, etc and that should be your lead-in as to your next actions. The symptoms can be from many causes and only testing can determine exactly what needs to be done.
I have a scheduled appointment for the 17th at the earliest. But I'm afraid it will go into limp mode going to work. I don't drive far most days today when I drove, it seemed fine minus the small fault after 20+ min of driving then after it seemed fine till the shift point changed.
 

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2007 GMC Sierra LBZ
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I would start checking ground connection points and yes by all means get the codes as they can be an indicator as to where to look.
 

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2018 GMC Sierra 2500 Denali HD
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Discussion Starter · #5 ·
I would start checking ground connection points and yes by all means get the codes as they can be an indicator as to where to look.
Publication Book Bookcase Font Shelving



And as you can see by the scroll bar there is a huge list of codes. Engine, Trans, brakes, camera, TPMS, glow plugs the list goes on. 35 codes between 7 different components some are duplicate such as P0700, U0073, U0101, U100 and more.
 

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Disconnect your batteries over night. Take both off and let it sit.

Sounds like you either bought a flood truck or bad ECM ground somewhere. Where is the truck from originally
 

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2018 GMC Sierra 2500 Denali HD
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Discussion Starter · #8 ·
Disconnect your batteries over night. Take both off and let it sit.

Sounds like you either bought a flood truck or bad ECM ground somewhere. Where is the truck from originally
Truck was built in flint, MI and was never registered out of MI. Carfax and all paperwork say it was owned by 2 prior owners and im the 3rd. No salvage title, no flood damage etc. Bought from a reputable dealership in the state.
 

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Hi I'm new to the diesel community and just bought a 2018 Denali HD Duramax 11 days ago. To the best of my knowledge no one prior to my ownership has done anything to the motor, transmission or exhaust. Yesterday I was driving normally when every light possible came on. 4wd fault, ABS fault, stibilitrack fault, power steering fault etc. Got home and truck would not start back up right away. Waited 30+ min and came back on with a solid check engine light. Today I drove it for maybe 1 hr and went into limp mode with all the dash lights coming on again. Check engine light has been solid the whole time and now 1/2 shifts late as if I was towing and 2/3shifts so hard it jerks the whole truck. Has about 142k and im not sure if I should bring to the dealership I bought it from (2hrs away) or to a local GM dealer. Any insight or help is very helpful. Thank you in advance!
With all the systems going bad and the transmission issues there is a digital communication issue. Disconnect the batteries and check ecu fuses also unplug the ecu connectors spray with contact cleaner check the pins an reassemble. Could also be bad grounds but worth checking the digital stuff first.
 

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With 142K on it, sure sounds like it's been Worked HARD. I think it should be way past due for a complete check-up.
Have you changed Oil & Filter, Air Filter, checked all fluid levels. I would flush the Tranny, change it's filter and refill with Syn Fluid.
 

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Start with the basics. Have your batteries and alternator load tested. I know it sounds simplistic, but weak batteries can cause a myriad of problems that can appear as more complex issues. BTW, have the batteries tested independently. One battery could be weaker than the other causing an overall lack of voltage/power.
 
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