ArrowsmithPML

You have bad quality DEF in the tank. Often it will go away when Temps warm up. If it doesn't, the tank will need to get drained.

You will be walking sooner than you think. You either fix (in some cases there is a warranty issue) or you rip it out and potentially get into other issues.

Diesels make all sorts of noise in the cold. But around -2 C / 30 F there shouldn't be any significant noise with the exception of the wrong fluids, lose filters (check the air filter seat and housing) and the fuel pump and filter (on the frame rail below the fuel filler location). These trucks need to be plugged in at -10 C to ensure the DEF tank doesn't freeze. I plug my '21 in for nearly 4 months straight but...

Yes. For both my 21 Yukon 3.0L and my 21 6.6L dmax. Dealer says no parts and we will call you.

Got the recall for my 3L yukon but not my 6.6L

What's wrong with it or do you know? I have a 2021 AT4 3500 and I've all sorts of DEF issues (mostly due to cold weather) but otherwise it's been pretty good.

Generally speaking, 10% of trailer. Then consider your payload. Then it depends on country and state/province and license and all that "stuff".

Hi, First off, although I do find it silly to save the environment, 1 jug at a time, the system does generally work ok. My issues are the repeated cold weather failures, regardless of tank fluid levels, being plugged in, having working heater elements etc. GM doesn't seem to under that this is their design problem and that owners like me are serious considering fixing it and in the process voiding warranties. I'm frustrated.

Find the part number from AC Delco and then do a cross match.

I've never had any problems with refueling in the cold. Usually the fuel gels up at -40 and your truck never shuts off. In slightly warmer periods, day-20C the retailer may give you a hard time. Sometimes fuel islands will issues you warnings too. The process is actually safe enough.

My 21 Yukon XL 3.0L Duramax has shuddered a few times with the auto stop/start when it restarts. I swear it is the torque converter. I have it going in on Wednesday so we will see what they find.

So at about -10 C and especially if I left I left the truck for a bit parked I would plug it in. Although not certain, my guess is that the transmission fluid and or oil sump and the associated circulation is cold and or not working. Just my initial thoughts.

Well if you build your own like me, they don't carry load as the relay does that. The relays in my case are under the hood and the switches trigger the relay.

Perhaps the $10k is high but in general operating costs are lower (maintenance can be costly) and even if fuel is more than regular you still get longer range, better efficiency and all kinds of other things I'm sure you've heard.

Yup... it sure does.

So now... a different problem - cracked heater core. Oh Joy. Parts on order...

Or just get off their high horse and recognize that it doesn't work and should be deleted.

Based on what I know of the tank, the filler neck and the system in general which is clearly not designed for this environment, the higher the volume in the tank, the less issue one has with the heater elements being exposed and useless and therefore less of an opportunity for freezing. I've had the filler neck freeze solid a few times before but it normally behaves itself with some warm air or one of those warm water under carriage truck washes (if one can be so lucky to get an oversized 3500 in there). I'm not new to diesels but everything I've owned was older than 2012 and didn't have this fool DEF. So, I too didn't fall off the turnip truck either. I will get to the bottom of this tomorrow but my patience is wearing thing. The coffee at the dealer isn't bad and it is warm inside so there is that... LOL...

I'm getting used to the coffee at the dealer - going back tomorrow. This time to pick up the 3.0L diesel Yukon (def tank sensors frozen today) and to drop off the 6.6L (again). This time, and new this afternoon the HVAC vents on either side of the steering wheel only provide cold air! Big issue when it's -30 outside. Getting frustrated... No CEL, I'm not going to bother running my scan tool as the dealer is 10 minutes away. They can do it. Cold weather like this sucks.

The fender mount plug powers electric heat elements on the DEF tank (apparently - I've not seen a wiring diagram). Does makes sense though.

Update: 2 of the 3 elements in the tank were melted prior to the TSB that was issued to replace the wiring harness and lower the amperage thru the wire. So when the 3rd element quit, the DEF fluid froze and the tank split open. Now, new harness, new tank and heating elements and I'm told to keep the tank full and the truck plugged in without a timer when below -15 C. Now, the wife's 3.0L is suffering from some kind of DEF sensor failure as the tank is full (added 20 L to it recently) and it is still showing near empty even after 5 hours of sitting in a heated shop. This DEF tank design is clearly flawed for cold weather.

Its a 2021. Do you have a TSB?

Well at this point that seems obvious. The dealer is keeping it over night

So it was -40C this morning and after getting my wife's '21 3.0L Yukon warmed up I elected to warm up the 6.6L and take it to get fuel. Got there, made the fill and upon restart, DEF tank warnings - DEF froze up. It has been in the heated shop all day and now it still has codes. It has previously survived -50 without issue so this is strange. Yes it is plugged in, has fuel conditioner and quality fuel.