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2021 DMAX - cold temp issues?

ArrowsmithPML

By ArrowsmithPML
in 6.6L Duramax Diesel (L5P)

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ArrowsmithPML Enthusiast

ArrowsmithPML

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So anyone with a 2020 or 2021 dmax that has had any issues with bitter cold winter starts?

Meaning, today it was -50C and trucks would obviously be plugged in. But does a GMC get the DEF tank frozen? 

What about high idles and running / idling for long periods. Any issues?

jaws3 Enthusiast

jaws3

Posted
Posted

Hi, have only had my 2021Duramax HC for couple of days but with the current cold spell of -50C in Manitoba I have had no issues with cold start. Forgot to plug it in 3 nights ago but it started next day without any issue (sleeps in unheated garage). I am very concerned about fuel consumption though. My 2017 Duramax LTZ was amazing at anything form 6.9l/100km (wife driving) to 8.7l/100km (my own heavier foot!) on highway trips. Around town it was an average of 11-14l/100km depending on how much warm-up idling I did. I am considering returning the 2021 to the dealer and taking back my 2017. As you can see on attached pic of 22 Jan 2021, these were real life numbers on my 2017 while using the "50km distance average" setting .198759240_IMG_20210122_07124232.thumb.jpg.1f7079bb5f06cce46699930f36209b3f.jpg. The new features in the HC are not worth sacrificing a perfectly good 2017 with only 54k on the clock and zero problems.

ArrowsmithPML Enthusiast

ArrowsmithPML

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You have a tier 4 diesel that sees less than 13L/100km and you are concerned? What is the new one getting? It won't get anywhere close to that on the computer in -30 or lower so I guess, please clarify.

Cheers,

jaws3 Enthusiast

jaws3

Posted
Posted

The consumption shown on the pic is from my 2017 LP5 that was traded. The HC LP5 I'm driving now only gives me 28 - 32l/100km on highway. And this was on a "special" highway run to see what I could get with just me and the wife, no cargo and feather-footing the pedal. I became so frustrated I abandoned the exercise after a while and just went home and parked it. In town consumtion is anything from 34l/100km to "off the charts". Not impressed but this is another topic not related to your original question - my answer which I hope shed some light on your question. And on that topic, I do find the 2021 taking longer to warm up the heater to make the cab comfortable. On a trip less than 13 minutes it barely heats up the cabin (again this is during the cold spell of -50C). That being said, the 2017 was faster at heating the cab in cold weather. 

ArrowsmithPML Enthusiast

ArrowsmithPML

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Wow! Idling my '12 Cummins RAM all day and I was only showing 31L/100km but that was just the display not the actual burn of fuel as that barely moved. So, if you are saying it was warm and got that actually driving, that's pathetic. I can see why you would be complaining. 

Perhaps there is something wrong with it? have you had it scanned? 

ArrowsmithPML Enthusiast

ArrowsmithPML

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I laugh about warming up in -50C. My truck took 45 minutes and 50km of driving and it barely hit 95 (middle of the gauge).

jaws3 Enthusiast

jaws3

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Posted
3 hours ago, ArrowsmithPML said:

Wow! Idling my '12 Cummins RAM all day and I was only showing 31L/100km but that was just the display not the actual burn of fuel as that barely moved. So, if you are saying it was warm and got that actually driving, that's pathetic. I can see why you would be complaining. 

Perhaps there is something wrong with it? have you had it scanned? 

It's going back to dealer on Tuesday as soon as they open after long weekend. After my earlier reply, I went out and did another 100km trip but consumption is atrocious. Something is wrong .

ArrowsmithPML Enthusiast

ArrowsmithPML

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No kidding. You've got bad injectors or a buggered computer that is doing something horrible for consumption.

Colossus Senior Enthusiast

Colossus

Posted
Posted

It's the cold weather to blame.  How many miles?  if new, still going thru break-in.  And yes there IS a break in period.

 

Colossus Senior Enthusiast

Colossus

Posted
Posted

Buuuuuut you are right.. there is something else at play.

 

jaws3 Enthusiast

jaws3

Posted
Posted

No regen message, no regen smell that I am used to with 2017 Duramax, no high idle that I used to have during regen on 2017. I don't think it is in regen mode but appreciate your input.

newdude Senior Enthusiast

newdude

Posted
Posted (edited)
On 2/9/2021 at 8:24 PM, ArrowsmithPML said:

So anyone with a 2020 or 2021 dmax that has had any issues with bitter cold winter starts?

Meaning, today it was -50C and trucks would obviously be plugged in. But does a GMC get the DEF tank frozen? 

What about high idles and running / idling for long periods. Any issues?

 

DEF tank and the DEF feed line to the injector are all heated.  DEF freezes as 11F/-11C.  It won't start DEF dosing until the DEF is un-frozen.  Fuel tank has a heater for the fuel as well.  Those are all ECM controlled, no "external" plugs.  

 

Long idling.  After the two attempts using the remote start, you'd have to turn it on, set the park brake and shift in to neutral.  These trucks have a run timer when in park to shut it off after 1/2 hour of idle time.  Leaving it in neutral overrides this timer.  

Edited by newdude
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CRApex Enthusiast

CRApex

Posted
Posted
On 2/9/2021 at 7:24 PM, ArrowsmithPML said:

So anyone with a 2020 or 2021 dmax that has had any issues with bitter cold winter starts?

Meaning, today it was -50C and trucks would obviously be plugged in. But does a GMC get the DEF tank frozen? 

What about high idles and running / idling for long periods. Any issues?

So my 2020 3500 in is right now for a DEF tank heater issue.  11,000 miles.  The heater is part of the tank assy so the tank needs to be replaced.  The dealer told me it was on back order and could be a month before they see it.  Truck is undriveable due to looming limp mode speed reduction so it sits at the dealer.  Otherwise it starts fine in the cold.

redwngr Senior Enthusiast

redwngr

Posted
Posted
On 2/14/2021 at 7:47 PM, jaws3 said:

The consumption shown on the pic is from my 2017 LP5 that was traded. The HC LP5 I'm driving now only gives me 28 - 32l/100km on highway. And this was on a "special" highway run to see what I could get with just me and the wife, no cargo and feather-footing the pedal. I became so frustrated I abandoned the exercise after a while and just went home and parked it. In town consumtion is anything from 34l/100km to "off the charts". Not impressed but this is another topic not related to your original question - my answer which I hope shed some light on your question. And on that topic, I do find the 2021 taking longer to warm up the heater to make the cab comfortable. On a trip less than 13 minutes it barely heats up the cabin (again this is during the cold spell of -50C). That being said, the 2017 was faster at heating the cab in cold weather. 

Maybe it's in regen, and can't get it done when it's -50C?

 

I thought MB was getting record cold?

How often did you run the 2017 in -50C? 

 

I'd be wanting to know how it does at -20C to 0C range before abandoning it.

Winter fuel doesn't help mileage, but it's certainly more than just a winter fuel issue.  

 

 

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