DEF system performance in Sub-Zero temps

[mbarber84]

Interesting observation this morning on DEF system performance in sub-zero weather…

Truck had been sitting for the past week outside. Weather has been unseasonably cold here with overnight lows at -8°F and highs during the day of about 15°F max. When I parked the truck, I had just above 1/4 tank of DEF (by the gauge on the instrument cluster) and the iDash was reading about 30ish % DEF fluid level. Plugged the block heater in last night and let it sit overnight. Started the truck via remote start at 6:40am this morning. Truck fired instantly, no waiting for the grid heater (due to it being warm enough from the block heater). Ambient air temp was -3°F. Truck went into high idle warm up cycle like normal. Got in the truck ten minutes later (6:50am) and the DEF gauge on the instrument cluster was reading just above 1/4 level, same as it was when I parked it a week ago. On the iDash however, the DEF level was showing 0% and DEF tank temp was only 12°F after ten minutes of run time. No codes and no messages.

I left for work, driving 15 minutes on the highway. Arrived at work and checked the readings again. Ambient air temp was about 4°F and DEF tank temp had risen to 14°F after a total of 25 minutes of run time. (Only increased about 2°F over the 15 minute drive). The DEF tank level still showing 0% on the iDash, but DEF level on the instrument cluster still was showing just above 1/4 full. Parked the truck and went to work. Still no codes or messages on the truck.

Fired truck up at 2:50pm to go home. Ambient air temp was now about 25°F. DEF tank level reading on the instrument cluster remained the same, but iDash was now showing the correct 31% tank level and DEF tank temp was 16°F.

We rarely see negative temperatures here in southwestern Pa so my experiences with the DEF system on these trucks in below 0°F situations is very limited. The few times we’ve seen that cold in the past, I didn’t have the iDash to be able to see more data. What I observed:

1. Significant variation between the instrument cluster DEF level and the data being pulled from the OBD using the iDash

2. In sub-zero ambient air temperature, after 10 minutes of engine run time, DEF tank temperature was only reading 15°F warmer than ambient, and was still below the threshold at which DEF will freeze.

3. In sub-zero ambient air temperature, after 15 minutes of drive time, DEF tank temperature was only reading 2°F warmer than when the truck left my driveway.

4. At no point did the truck register any system error messages, nor did it trigger any pending or active DTC’s.

5. Standing outside the truck, while it was in high idle mode, I could tell that the DEF doser was not injecting fluid as it normally would be. I’m assuming this performance would indicate the software will inhibit DEF dosing until the fluid is warm enough to begin flowing. It was dosing in the afternoon when I left work to head home.

 

[Deleted member 47449]

The DEF at 12F probably didn't freeze. That's the stated freezing point for DEF though. I store 3 cases of Blue DEF on a table inside our home's attached 24' x 24' unheated garage which shares an interior wall. It usually stays around 10F inside the garage when it's much colder outside at below zero. Haven't found the DEF stored in the garage ever frozen. My beer cans though are solid ice.

 

[Brutal_HO]

Interesting observation this morning on DEF system performance in sub-zero weather…

Truck had been sitting for the past week outside. Weather has been unseasonably cold here with overnight lows at -8°F and highs during the day of about 15°F max. When I parked the truck, I had just above 1/4 tank of DEF (by the gauge on the instrument cluster) and the iDash was reading about 30ish % DEF fluid level. Plugged the block heater in last night and let it sit overnight. Started the truck via remote start at 6:40am this morning. Truck fired instantly, no waiting for the grid heater (due to it being warm enough from the block heater). Ambient air temp was -3°F. Truck went into high idle warm up cycle like normal. Got in the truck ten minutes later (6:50am) and the DEF gauge on the instrument cluster was reading just above 1/4 level, same as it was when I parked it a week ago. On the iDash however, the DEF level was showing 0% and DEF tank temp was only 12°F after ten minutes of run time. No codes and no messages.

I left for work, driving 15 minutes on the highway. Arrived at work and checked the readings again. Ambient air temp was about 4°F and DEF tank temp had risen to 14°F after a total of 25 minutes of run time. (Only increased about 2°F over the 15 minute drive). The DEF tank level still showing 0% on the iDash, but DEF level on the instrument cluster still was showing just above 1/4 full. Parked the truck and went to work. Still no codes or messages on the truck.

Fired truck up at 2:50pm to go home. Ambient air temp was now about 25°F. DEF tank level reading on the instrument cluster remained the same, but iDash was now showing the correct 31% tank level and DEF tank temp was 16°F.

We rarely see negative temperatures here in southwestern Pa so my experiences with the DEF system on these trucks in below 0°F situations is very limited. The few times we’ve seen that cold in the past, I didn’t have the iDash to be able to see more data. What I observed:

1. Significant variation between the instrument cluster DEF level and the data being pulled from the OBD using the iDash

2. In sub-zero ambient air temperature, after 10 minutes of engine run time, DEF tank temperature was only reading 15°F warmer than ambient, and was still below the threshold at which DEF will freeze.

3. In sub-zero ambient air temperature, after 15 minutes of drive time, DEF tank temperature was only reading 2°F warmer than when the truck left my driveway.

4. At no point did the truck register any system error messages, nor did it trigger any pending or active DTC’s.

5. Standing outside the truck, while it was in high idle mode, I could tell that the DEF doser was not injecting fluid as it normally would be. I’m assuming this performance would indicate the software will inhibit DEF dosing until the fluid is warm enough to begin flowing. It was dosing in the afternoon when I left work to head home.

Correct assumption. I've never had a DEF issue in below (well below) 12F ops. You get a "pass" if it's frozen. I think where you might see trouble is if the ambient is above freezing for xx time and the DEF isn't flowing because it's a giant block of ice and the heater isn't thawing it, trouble codes will follow.

In fact, there was a TSB for some early (19?) trucks to correct the code for that. Seems they didn't have it right first time out of the gate and they were throwing excess codes. I believe before his truck went all Jenny Craig @H3LZSN1P3R went through that.

 

[AH64ID]

Sounds completely normal for what I have seen.

I’ve noticed that the DEF heater doesn’t work unless ambient temp is above 12°F, my guess is since the DEF injector line is exposed.

You shouldn’t see any codes. At those cole of temps the emissions standards exempt us from DEF use.

I’ve also seen 0% with a frozen DEF tank. The way the sensor works it can’t read volume correctly when frozen. The dash is likely programmed to remain constant with low temps. That being said I’ve found the DEF level PID to be inaccurate and not worth monitoring at any temp.

Does the iDash not have the parameters to show DEF injection pressure and/or injection percentage?

 

[MegaRed]

My beer cans though are solid ice.

You need to buy beer with a higher alcohol content!

 

[mbarber84]

Sounds completely normal for what I have seen.

I’ve noticed that the DEF heater doesn’t work unless ambient temp is above 12°F, my guess is since the DEF injector line is exposed.

You shouldn’t see any codes. At those cole of temps the emissions standards exempt us from DEF use.

I’ve also seen 0% with a frozen DEF tank. The way the sensor works it can’t read volume correctly when frozen. The dash is likely programmed to remain constant with low temps. That being said I’ve found the DEF level PID to be inaccurate and not worth monitoring at any temp.

Does the iDash not have the parameters to show DEF injection pressure and/or injection percentage?

The DEF supply line from the tank to the doser / injector is also heated. There’s an electric trace wire element wound around it. So it should be heating there as well.

As far as I can find, the iDash doesn’t show DEF injection pressure or injection percentages but I could submit those as possible additions for a software update. I’ve already done that for a few others it doesn’t show.

 

[H3LZSN1P3R]

Correct assumption. I've never had a DEF issue in below (well below) 12F ops. You get a "pass" if it's frozen. I think where you might see trouble is if the ambient is above freezing for xx time and the DEF isn't flowing because it's a giant block of ice and the heater isn't thawing it, trouble codes will follow.

In fact, there was a TSB for some early (19?) trucks to correct the code for that. Seems they didn't have it right first time out of the gate and they were throwing excess codes. I believe before his truck went all Jenny Craig @H3LZSN1P3R went through that.

Yes, my truck would try and use DEF before it was thawed enough and cause the crystallization on the pump blocking the flow even after the DEF was thawed which caused the limp mode count down many times. I would have to remove the pump and clean it. this was typically in the -25°C to -45°C range when the issues would arise. as-well as the level sensors had issues. My truck actually still has the issues as I had reinstalled the emissions in October but removed them again at the end of December since the Def issues arised again and Ram stopped the 90A recall And only made it a extended warranty.

The one time I actually monitored the DEF temp it -43°C and after a 3 hr drive the DEF temp increased 1 degree! The tank heaters are not great is my conclusions. We would need an insulated tank with a bigger heater for efficient results

 

[Great White North Eh]

The trucks should have a disclaimer plaque saying ‘’truck may not operate in cold climate conditions’’. They could mount it on the console lid like the numbered editions. That would build customer confidence. Good engineering …hang a plastic tank down in the wind and snow filled with a water based liquid …brilliant!

 

[Blackpowder]

The DEF supply line from the tank to the doser / injector is also heated. There’s an electric trace wire element wound around it. So it should be heating there as well.

As far as I can find, the iDash doesn’t show DEF injection pressure or injection percentages but I could submit those as possible additions for a software update. I’ve already done that for a few others it doesn’t show.

I use obd mx+ and there is a standard SAE PID for commanded DEF dosing (%). I also found 3 different PIDs for DEF tank level. One is a standard SAE PID, and two are Ram unique. I tried all three, but can't remember if they all worked. They may work different under the cold weather condition you experienced. I am currently linked to the Ram Bussed PID.

 

[Deleted member 47449]

Just checked this morning and it's at 11F in our garage which is much warmer than outside. That's pretty close to the 12F minimum storage recommended. I'm not bringing the urea inside the house for warmer storage unless it's necessary.

 

[AH64ID]

The DEF supply line from the tank to the doser / injector is also heated. There’s an electric trace wire element wound around it. So it should be heating there as well.

Good to know, thanks!

The one time I actually monitored the DEF temp it -43°C and after a 3 hr drive the DEF temp increased 1 degree! The tank heaters are not great is my conclusions. We would need an insulated tank with a bigger heater for efficient results

Based on what I saw it doesn’t try to thaw a frozen tank if it’s below 12°F. I saw no temp rise on a couple hour drive starting below 0°, but in a very short amount of time the tank was above 20° once the ambient temp got above 12°

Pretty sure my tank will be a DEF block in a couple days so I’ll monitor temps again.

 

[mbarber84]

Good to know, thanks!



Based on what I saw it doesn’t try to thaw a frozen tank if it’s below 12°F. I saw no temp rise on a couple hour drive starting below 0°, but in a very short amount of time the tank was above 20° once the ambient temp got above 12°

Pretty sure my tank will be a DEF block in a couple days so I’ll monitor temps again.

Wouldn’t it be nice if they would just provide us a free resource available online where we could read the program logic that controls all of this stuff? I don’t understand why these manufacturers treat this stuff like it’s gold or some big secret.

 

[Deleted member 47449]

With our 2024 Ram 6.7L engine running with frozen DEF, it means more pollution in the air. This increase in emissions may make it warmer than below 12F outside during our winters. Maybe it's a good thing.

DEF in Cold Weather: At What Temperature Does DEF Freeze? - Fuel Logic

Learn expert fuel safety precautions and guidelines for handling fuel. Ensure safety and minimize risks with our comprehensive tips and advice.

www.fuellogic.net

 

[Lerker]

I dunno fellas, cause a couple weeks back I fired her up in 5* weather.... 10 minutes down the highway (towing the 5ver, if that matters), I got the Service DEF System See Dealer message. Kept driving, and about 10 minutes after that got the Speed Limited message. Pulled into the nearest truck stop and let the sun bake the truck. Also put warm DEF in the tank. After an hour, started her up the the message cleared. Haven't gotten it again.

I assumed the tank was frozen and not thawing quick enough, which triggered the messages.

 

[H3LZSN1P3R]

With our 2024 Ram 6.7L engine running with frozen DEF, it means more pollution in the air. This increase in emissions may make it warmer than below 12F outside during our winters. Maybe it's a good thing.

DEF in Cold Weather: At What Temperature Does DEF Freeze? - Fuel Logic

Learn expert fuel safety precautions and guidelines for handling fuel. Ensure safety and minimize risks with our comprehensive tips and advice.

www.fuellogic.net

View attachment 81653

Less DEF used means more EGR use which is bad for the engine soooooo I dint like that theory

 

[Brutal_HO]

I dunno fellas, cause a couple weeks back I fired her up in 5* weather.... 10 minutes down the highway (towing the 5ver, if that matters), I got the Service DEF System See Dealer message. Kept driving, and about 10 minutes after that got the Speed Limited message. Pulled into the nearest truck stop and let the sun bake the truck. Also put warm DEF in the tank. After an hour, started her up the the message cleared. Haven't gotten it again.

I assumed the tank was frozen and not thawing quick enough, which triggered the messages.

Practical or not, the potential for this is why my DEF tank is never filled, and left low as much as possible in the winter. My routine is and always has been add a 2.5 gal jug when it's 1/4. Sure, the smaller volume will freeze solid quicker than a larger volume, but at least I have room to add DEF if needed - if it even matters.

 

[AH64ID]

Wouldn’t it be nice if they would just provide us a free resource available online where we could read the program logic that controls all of this stuff? I don’t understand why these manufacturers treat this stuff like it’s gold or some big secret.

Would be awesome.

With our 2024 Ram 6.7L engine running with frozen DEF, it means more pollution in the air. This increase in emissions may make it warmer than below 12F outside during our winters. Maybe it's a good thing.

DEF in Cold Weather: At What Temperature Does DEF Freeze? - Fuel Logic

Learn expert fuel safety precautions and guidelines for handling fuel. Ensure safety and minimize risks with our comprehensive tips and advice.

www.fuellogic.net

View attachment 81653

These engines already make really low NOx emissions, I’m not concerned in the least.

Less DEF used means more EGR use which is bad for the engine soooooo I dint like that theory

Next time my DEF freezes I’ll monitor EGR use.

 

[Deleted member 47449]

Practical or not, the potential for this is why my DEF tank is never filled, and left low as much as possible in the winter. My routine is and always has been add a 2.5 gal jug when it's 1/4. Sure, the smaller volume will freeze solid quicker than a larger volume, but at least I have room to add DEF if needed - if it even matters.

I do the same with our 2024 Ram HO Cummins. Wait until it's 1/4. Puts it at 3/4 with a 2.5 gallon jug. DEF expands when frozen and it can break the tank. The less DEF in the tank the easier for it to be heated and thawed out.

I've had a new truck's windshield wiper fluid full reservoir freeze in below negative 40 Fahrenheit temperatures and it broke. The DEF tank probably costs a lot more to replace.

 

[mbarber84]

Practical or not, the potential for this is why my DEF tank is never filled, and left low as much as possible in the winter. My routine is and always has been add a 2.5 gal jug when it's 1/4. Sure, the smaller volume will freeze solid quicker than a larger volume, but at least I have room to add DEF if needed - if it even matters.

I do the exact same thing
The old 1/4 to 3/4 swing.
I assumed the volume would freeze fast but also be less to thaw. Doesn’t seem like the electric heater is anywhere near as potent as I thought it would be. I’m finding more and more each day that investing in this iDash was a good move. There’s a lot we “miss” operating these with just the factory instrumentation. I’ve heard that ignorance is bliss, and that might be true in a lot of things, but I’m not sure it’s the best MO when it comes to these trucks.

 

[mbarber84]

I do the same with our 2024 Ram HO Cummins. Wait until it's 1/4. Puts it at 3/4 with a 2.5 gallon jug. DEF expands when frozen and it can break the tank. The less DEF in the tank the easier for it to be heated and thawed out.

I've had a new truck's windshield wiper fluid full reservoir freeze in below negative 40 Fahrenheit temperatures and it broke. The DEF tank probably costs a lot more to replace.

In theory, even if the tank was “Full” (at its rated capacity), it should have room to expand because the tank’s actual physical volume is larger than its rated capacity. That being said, it’s very difficult to know when it’s actually “full” when filling unless you’re very closely and slowly monitoring the gauge on the dash. Where a lot of people get into trouble is when they’re filling the tank from a bulk tank and pump. It’s easy to overfill it in that case. Ram actually put out a TSB on this several years ago because they were seeing so many cold weather performance issues with the system.
DEF freezing solid inside the filler neck from overfilling was one of the points. I have stuck with the 1/4 to 3/4 practice since the day I took delivery of both my 2017 and now this 2022 and it has never failed me yet.