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Limp Mode 2020 Denali 3500

In2racn
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In2racn Enthusiast

In2racn

Posted
Posted (edited)

I am ready to burn this $80000 POS. 6000 miles on the truck. On the way to Quebec to ride sleds, the thing starts jerking, downshifting, falling into a fake neutral, just running terrible. Then the dash says "Engine power reduced" and I am only able to do 20 mph. I "reboot" the truck and get power back, but it is still jumping around, downshifting, all kinds of weird stuff. The next dash notification says Diesel Exhaust error.... limited to 65 in 170 miles. So now I am 300 miles from, limited to 65 and  I am not sure if it will even make it home. 

 

I left my code reader home.... not exactly sure what the error is.  I am wondering if I stop at a GM dealer on the way home, if they clear the code, will I get full speed back?

 

Anyone with similar issues.

Edited by In2racn
Colossus Senior Enthusiast

Colossus

Posted
Posted

No they cannot clear it thru onstar.  Yes they can clear it at the dealer but some dealers might not want to

MrGraff Enthusiast

MrGraff

Posted
Posted

Could always try the unhook batteries method let it sit couple of hours unhooked, and then try it out.  Almost sounds like transmission related the way your talking.  

  • 2 weeks later...
In2racn Enthusiast

In2racn

Posted
  • Author
Posted

to follow up on this issue...  I rode sleds for 4 days, jump into the truck to head home, CEL is on. I kept waiting to get additional dash messages that would say "Speed limited in XXX miles" as it did before I shut it down for a few days, but nothing. The truck was running fine. 

 

About 150 miles in, the check engine light went out and all was normal. Took it to the dealer, the truck has a "shorted" manifold sensor. They replaced the sensor and all seems fine.

 

Today, driving along with the DEF gauge showing over half a tank of DEF. Suddenly, the dash message says "DEF empty in 1000 miles" . One second later "DEF empty in 471 miles". next second "DEF empty in 39 miles". and again one second later "DEF LOW, Speed limited soon"

 

Moral of the story, carry DEF with you. The gauge is useless and may go to empty in seconds without warning.

 

The 2020 has me REALLY missing my deleted 2011.

MrGraff Enthusiast

MrGraff

Posted
Posted
15 hours ago, In2racn said:

to follow up on this issue...  I rode sleds for 4 days, jump into the truck to head home, CEL is on. I kept waiting to get additional dash messages that would say "Speed limited in XXX miles" as it did before I shut it down for a few days, but nothing. The truck was running fine. 

 

About 150 miles in, the check engine light went out and all was normal. Took it to the dealer, the truck has a "shorted" manifold sensor. They replaced the sensor and all seems fine.

 

Today, driving along with the DEF gauge showing over half a tank of DEF. Suddenly, the dash message says "DEF empty in 1000 miles" . One second later "DEF empty in 471 miles". next second "DEF empty in 39 miles". and again one second later "DEF LOW, Speed limited soon"

 

Moral of the story, carry DEF with you. The gauge is useless and may go to empty in seconds without warning.

 

The 2020 has me REALLY missing my deleted 2011.

This was actually a problem with previous l5p, and was resolved with a computer flash.  I bet youd find it wouldnt take much def.

cNate Enthusiast

cNate

Posted
Posted

I had the same with the DEF, I keep some in the bed at all times now. Mine said 1k miles left. At about 300 miles later, it gave me the low DEF warning and said it would limit speed soon. I was towing a trailer through the desert and had fortunately made it through about a 200 mile stretch already where I would not have been able to get more. Grabbed some about 10 mins after the low warning and it took 2 2.5 gal and said full. That was about 1k miles ago. It’s showing it’s about 1/3 full on the gauge now. Seems this truck either blows through 7.5 gals every 2k miles or the gauge is off.

How many miles should you get on a full tank of DEF?


Sent from my iPhone using Tapatalk

Cool J Enthusiast

Cool J

Posted
Posted

The consumption of DEF will vary depending on how hard the truck is working. I just returned from a 2,000 mile trip towing my fifth wheel and used about 5 gals. Now that I'm back home and used another 1,000 miles running around town the gauge has only gone down one bar. This mirrors what my 2016 consumed.

  • Like 1
tima0101 New Member

tima0101

Posted
Posted

My 2020 is doing the exact same thing.  Erratic driving, same warnings, engine light came on then next day it was off.  I even got the same DEF notice with a full tank of DEF.  7,000 miles on mine.  I am wondering if this is related to cold conditions as I'm in Alaska and you're in Quebec.

 

  • 5 months later...
Tj1227 New Member

Tj1227

Posted
Posted

My 2020 has 7000 miles on it and just showed up today with a message that says “ 175 miles until 65mph max”. Thought it might have been low on DEF but filled it up and message still appears and miles are counting down.

gearheadesw Senior Enthusiast

gearheadesw

Posted
Posted

Well, was thinking about a long bed diesel, WAS.

Obviously the new diesels are still junk with the def system.

What a total bummer for those who where told " all is good now with the def system"

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