DEF gauge delay

[Roger Nolter]

Did my first DEF fill up yesterday. 2,000 miles on 1/2 tank. After I filled it up I turned the engine on and instead of the gauge acting like the fuel gauge and going to full, it took its sweet time intermittently going up to full. Why does this gauge act like that? Anyone seeing the same thing? Truck is a new ‘22 2500 bought a month ago.

 

[Rob S]

Normal

 

[Roger Nolter]

Normal

Thank you Rob

 

[SBashaw]

If I remember right, it stated somewhere in the owners manual that it would be slow to correct itself. Not sure why.

 

[AH64ID]

It doesn’t have a float like a fuel tank, but rather sensors that are more similar to a RV storage tank. It’s slow to fill and slow to drain at first. There is a programmed delay.

 

[SBashaw]

Slosh delay

 

[Cummins12V98]

My 15 has never done anything like that and has always acted like a fuel tank.

 

[Roger Nolter]

If I remember right, it stated somewhere in the owners manual that it would be slow to correct itself. Not sure why.

It sure does on page 221. I’ve only reached page 144 so far. Says the “DEF gauge may take up to 5 seconds to update after adding a gallon or more.” Thanks for the help!

 

[Turbo Terry]

Mine came up pretty fast.

 

[R.Taylor]

I think some of it has to do with it crystalizing on the inside of the tank, when the tank is low or near empty it gives the DEF a chance to crystallize.... on the non wetted surfaces, When you fill it up and wet the crystals... They dissolve, Which in turn sensors start working normally.

My 2 cent theory

 

[Roger Nolter]

I think some of it has to do with it crystalizing on the inside of the tank, when the tank is low or near empty it gives the DEF a chance to crystallize.... on the non wetted surfaces, When you fill it up and wet the crystals... They dissolve, Which in turn sensors start working normally.

My 2 cent theory

Definitely plausible. It’s what I was thinking. I only went to 1/2 then filled. But the upper half was certainly dry. I wonder if the tank has a coating to minimize it?

 

[sag2]

The new trucks use a different type of sensor than the 18 and older trucks. They now use an ultrasonic frequency signal and need an air gap for the sensor signal to return. The older trucks used a Radio Frequency, or RF signal that sent low frequency waves thru the fluid to measure level.
Overfilling a 19+ truck may result in a P203E because without an air gap at the top of the tank the signal will not return to the sensor properly.

 

[R.Taylor]

"Overfilling a 19+ truck may result in a P203E"

Yep... learned that one hard way. Topped off the DEF to the fill neck once... Threw the code and limp mode countdown started. Luckily I was able to get enough out for the code to clear itself after driving a bit.

 

[Cummins12V98]

I like filling BOTH tanks to the top. Another reason to keep the “OLD 15”

 

[bcbender]

I simply just use the bulk pumps at the truck stops and fill it till it "clicks" off. always around 4 gal from when the gauge is ready to touch the red area (around 1/4) and seems to work for me.

 

[Turbo Terry]

New 2022 3500 ho aisin srw went 4000 k on one full tank of def. Some city hiway and heavy hauling