Well DEF gremlin wins again

I have one of those Friday or Monday made trucks that always shows full on the DEF.

the next time I take it in I’ll add it to the list for them to check out.

I posted about this before and a lot of folks say”wait til you get the 500 miles of DEF remaining warning before adding anything.

So this week…while the gauge shows full, I got the 500 mile warning.

so I decide to just add 1 2.5 gallon container. Thinking to leave it on the low side for cold weather expansion.

welll, 1 gallon into the fill, the DEF tank topped off.

so now, I have no room for cold weather expansion.

DEF gremlin wins again.

 

My '22 450 does the same thing with the gauge. Had Ford look at it while it was there last time and they gave me some crap about it working normal and it learns your driving style and habits and adjusts the range from there.

 

Get an iDash, it tells you the percentage in the tank. It also has pids to see it's use, when it fires etc.

 

What does the iDash use for a sensor? If it is the same sensor that is already causing problems, how does it help?

 

Something is telling the truck it is low on DEF, and the iDash will show percentages based on the in tank sensor. Where the dash would show it full, if it is actually 80% it will show full on the dash, but the actual percentage on the iDash. I think there are a few other option on the idash, but I haven't used them, only the tank level which is very accurate.

With the iDash, if the truck says 500 to empty, but the iDash shows 80%, then the dealer cannot say that it is working fine, can they? They have to then prove it, hand them the jug and ask to fill it while you watch, and when only a gallon goes in, you say, and you were saying that's normal? Doesn't the tank hold like 7 or so gallons? Put THEM on the spot. Something is wrong if it prompts 500 miles to empty with 6 gallons still in the tank.

 

I had the same thing happen - maybe a bit different.....
Gauge showed 3/4 and I getting 500 miles to empty message; then 400 miles to empty; and so on until it was at 50 miles to empty - all the while with the gauge and ForScan showing 3/4.

I filled the tank and it only too about 2 or 3 gallons (hardly as much as I expected). Then the gauge showed 100% (and so did ForScan) and the DEF read out on the dash read 9000 miles to empty.

I took it to Ford, they did some software "thing" and gave me the same 'stuff' about the truck is learning....., the dash display (somewhere in the Engine info section) then showed 7500 miles to empty and the gauge was still on full (100%).

After driving - a lot - the gauge finally went down and seems to be operating normally. I've filled again and it seems the right amount went in the tank and the gauge operated as I expected.

I'm not sure whatever Ford did actually changed or fixed anything, but I now have a more updated software load for that gauge and feel things are working OK.

I have a post about it somewhere else on this forum with some photos.

 

Sounds like the gauge IS WORKING, because if it only took one gallon to fill it all the way up, then the gauge should have shown full.
Gauge will show full until 1.5 gallons or more have been used.
So, the issue is the fact that it is saying 500 miles to empty on a full DEF tank, so some sensor has shown faulty info to the pcm.
The 500 mile warning may correct itself with more use, more restarts.

 

Normal DEF consumption is 1-2 percent of the fuel burned. If it is more than that there is a problem with the NOx sensor in the truck. How much DEF is burned is based on the amount of diesel burned and not the mile driven. When towing my mpg drops by 20% and so my DEF consumption increases by 25% for the same number of miles driven.

DEF has a freezing point of 12 degrees but doubt its expansion if frozen will cause problems. DEF is 67% water and water expands by 9-10 percent when frozen and the DEF tank is air tight to restrict expansion.