DEF Tank - Frozen

ArrowsmithPML · December 20, 2022

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.

Brianibew · December 21, 2022

There is a heater in the def tank. It may have failed.

ArrowsmithPML · December 21, 2022

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

gemarsh · December 21, 2022

What year? There is an updated tsb for the early 22's and back. Had to do with a bad electrical connector for the def tank that would melt.

ArrowsmithPML · December 21, 2022

Its a 2021. Do you have a TSB?

Edited December 22, 2022 by ArrowsmithPML
formatting

ArrowsmithPML · December 21, 2022

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.

gemarsh · December 22, 2022

2 things. What good reason did they give you for plugging the block heater in, since def tank is electrically heated and not coolant heated?

2nd, how will a full def tank help from freezing and breaking the tank? Closer to empty for expansion of frozen piss water makes more sense. But then again, I didn't stay at a holiday inn last nite. ;>)

ArrowsmithPML · December 22, 2022

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

ArrowsmithPML · December 22, 2022

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.

ArrowsmithPML · December 22, 2022

1 hour ago, gemarsh said:

2nd, how will a full def tank help from freezing and breaking the tank? Closer to empty for expansion of frozen piss water makes more sense. But then again, I didn't stay at a holiday inn last nite. ;>)

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...