2020 duramax putting me in reduced power mode!

BBE · February 18, 2021

I've got a 2020 Denali HD with 44k miles on it and this is the second time now that I have gotten a service def code. This time they told the the def heater was bad. It's part of the tank and evidently you have to change the whole tank.

There is literally no availability on these ANYWHERE. I'm being told no dealerships in the country have them. There is a single one at a dealership in Illinois but they won't sell it because it's for one of their customers and they have had at least 95 calls on it trying to buy it.

So basically I have an 80 thousand dollar truck that I can't drive for who knows how long... Could be months. This is ridiculous.

I still have about 50 miles left before it puts me in reduced power mode and limits me to 65mph.

So part of my post was just to vent and see if anyone else has suggestions for me. And the other part is to ask how this reduced power mode works. I mean I could live with 65mph I guess for a while. Is it gonna stay there? Will it get worse and keep throttling me back? How quick? I have never had to test the waters on it.

Any advice is appreciated!

brclark82 · February 18, 2021

I know this isn’t much help but on the Facebook L5P page I have seen multiple people mention this exact problem and back order issues with no dates being given for availability...sorry about that, good luck

CRApex · February 18, 2021

5 hours ago, BBE said:

I've got a 2020 Denali HD with 44k miles on it and this is the second time now that I have gotten a service def code. This time they told the the def heater was bad. It's part of the tank and evidently you have to change the whole tank.

There is literally no availability on these ANYWHERE. I'm being told no dealerships in the country have them. There is a single one at a dealership in Illinois but they won't sell it because it's for one of their customers and they have had at least 95 calls on it trying to buy it.

So basically I have an 80 thousand dollar truck that I can't drive for who knows how long... Could be months. This is ridiculous.

I still have about 50 miles left before it puts me in reduced power mode and limits me to 65mph.

So part of my post was just to vent and see if anyone else has suggestions for me. And the other part is to ask how this reduced power mode works. I mean I could live with 65mph I guess for a while. Is it gonna stay there? Will it get worse and keep throttling me back? How quick? I have never had to test the waters on it.

Any advice is appreciated!

I hear ya..mine is in the shop now with no time frame for the part to arrive. I was told that once it hits the 65 mph threshold, soon thereafter it will reduce to a crawl. Bottom line is they are not driveable once that tank heater goes. Extremenly frustrating to say the least. 11,000 on mine

On a side note, I was given a print out of every dealer in the country that shows them in stock...I called every one in hopes I would get lucky. NOPE, all spoken for. A couple dealers told me it took 2 weeks and others have said they've been waiting 6 weeks. Sure wish they offered a 10spd with the 6.6 gas, I might actually give that a chance given this situation.

Edited February 18, 2021 by CRApex

CMillSilverado · February 18, 2021

I wanted the 6.6 gas but ended up getting a Duramax since they don't make Gas in higher trims unless you order and thats as bad as trying to find parts like this. I'm assuming they gave you a loaner, not sure how they make something like this right?

I had a 17' Duramax and had the heater go out once which they fixed and the DPF go into reduced power 3 times which they did nothing for. The DPF would eventually fix itseld but no go with heater. I'm crossing my fingers I don't have these issues with this new 21'

redwngr · February 18, 2021

They are building 1000's of new HD's every week.

There is no acceptable excuse for not redirecting def tanks to existing customers.

Laidback · February 18, 2021

1 hour ago, redwngr said:

There is no acceptable excuse .

$$,$$$$

Basketcase · February 19, 2021

Just got my truck back last week after being at the dealer for 3 weeks with a bad DEF heater. My truck ended up being the guinea pig for a fix they wanted to try until the part comes in. They spliced two wires together that should not work together but did it anyways against GMs wishes. It has been working flawlessly for the last week and my dealer asks for an update everyday to keep GM engineers in the loop. My truck was the first they had seen with the problem... now some dealers around here have 20+ trucks sitting in their lots with the same issues.

I have a $100k truck and own a business that I use it for everyday to haul. This was a big pi$$ off to me that GM couldn't fix the problem. My part was ordered weeks ago and was canceled by GM because they had so many failures coming in they are going to try and redesign the part before sending them out I am told. Sounds like a recall will be coming. I'm just happy that my dealer chose me to be the guinea pig because my loaner (at first it was a Terrain which I told them didn't work for my job, and they gave me a 1500 a couple days later which helped a bit) wasn't cutting it for what I bought my truck to do.

Also, I drove it in reduced power at 104km/hr (65mph) which was good for about 100 miles or so, and then it alerted me that it would reduce again to 88km/hr (55mph) which is barely the speed limit on the side roads, and less than the speed limit on our highways... if it didn't keep dropping the Max speed, I would have advised you guys to keep it until there was a fix... but it doesn't work that way unfortunately

cNate · February 19, 2021

Can you do a DEF system delete? Are you in a state that requires it?

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Colossus · February 19, 2021

You can't do a DEF or DPF delete if you don't have the tuner/programmers needed, and the EPA shut down all the known tuners that were providing those.

jeetS · February 20, 2021

Basketcase,

If that works I'm sure there would be a lot of people curious on what was done to get it to work!

BBE · February 20, 2021

19 hours ago, Basketcase said:

Just got my truck back last week after being at the dealer for 3 weeks with a bad DEF heater. My truck ended up being the guinea pig for a fix they wanted to try until the part comes in. They spliced two wires together that should not work together but did it anyways against GMs wishes. It has been working flawlessly for the last week and my dealer asks for an update everyday to keep GM engineers in the loop. My truck was the first they had seen with the problem... now some dealers around here have 20+ trucks sitting in their lots with the same issues.

I have a $100k truck and own a business that I use it for everyday to haul. This was a big pi$$ off to me that GM couldn't fix the problem. My part was ordered weeks ago and was canceled by GM because they had so many failures coming in they are going to try and redesign the part before sending them out I am told. Sounds like a recall will be coming. I'm just happy that my dealer chose me to be the guinea pig because my loaner (at first it was a Terrain which I told them didn't work for my job, and they gave me a 1500 a couple days later which helped a bit) wasn't cutting it for what I bought my truck to do.

Also, I drove it in reduced power at 104km/hr (65mph) which was good for about 100 miles or so, and then it alerted me that it would reduce again to 88km/hr (55mph) which is barely the speed limit on the side roads, and less than the speed limit on our highways... if it didn't keep dropping the Max speed, I would have advised you guys to keep it until there was a fix... but it doesn't work that way unfortunately

Basketcase,

I showed this post to my dealership, and they wanted to know if it would be possible to get some more information on this? Perhaps the name of your dealership so that they can contact them? Or a picture of the two wires jumped? Or a description of the process? We're dying for anything about this possible fix! You can PM me the info if you want to leave it off the public forum.

Thanks!

silveradosid · February 20, 2021

does anyone know what the dealership does with the old tank after they replace with a new one

hollywoodsle · February 20, 2021

3 hours ago, silveradosid said:

does anyone know what the dealership does with the old tank after they replace with a new one

All warranty parts are held on to by the dealer for a certain amount of time. If GM decides they want the part back for whatever reason, the dealer ships it back to GM. If GM does not want the part back they are thrown away.