[mdonnelly4749]

I must have a stuck DEF level sensor in my 2018 5.0L. The DEF level in the OBD2 tool show 100%, but when I added DEF fluid it took the whole 2.5 gallons. I was suspicious because the limp mode warning came on for a day, and then went away.
Has this happened to anyone else, and can it be fixed (easily)?

 

[Two Yeets]

Our DEF sensors are shit, and I believe they're used on another truck. Maybe it's the Ram, but who knows. One issue we often have is bubbles getting caught on the sensor, throwing off the reading. Beating the tank can often release these bubbles, or you can delete the truck for about $1000 and never have emissions problems again.

 

[NavyCuda]

Basically all of the emissions components should be considered consumables. They're exposed to extreme heat and corrosive chemicals to do the job they do. If you're in a jurisdiction that allows it, deleting is the best choice.

 

[J Casper]

My 2017 DX just went to the dealer for this DEF warning. On Sunday morning (after a big temp drop) the DEF warning showed up. The dealer called, and they want to replace the knock sensor. Hoping the extended warranty will cover the costs

 

[JasperQuick]

Had the same issue on mine outside temp was near zero one night and when I started the truck that morning the DEF light came on a few minutes later the going into Limp Mode in 250 miles message pop up. Had to drive it 15 miles to work because dealer wasn't open that early. Took it in that afternoon to the dealer which was 10 miles from work. On the way over to the dealer the light and warning both went out. I was told the tank has a heater strip to keep the DEF from freezing but it only works when the truck was running. Since the temp during the day had got above freezing and I had parked where the sun was shinning on that side of the truck the DEF tank thawed out which is why my warnings cleared.

At the same time I was told by the service manger at the dealership that unlike the fuel tank there is no float in the DEF tank that the truck estimates amount of DEF and what shows up on the gauge is an estimate not actual. He said it has a sensor that when the DEF gets below that level the DEF Warning comes on. I have had the DEF gauge on a trip show 100% and within 200 miles the light come on and says I have 40% left. The DEF tank holds 4.5 gallons and I have put the whole 2.5 gallon jug and over a 1/3 of another jug in! I was also told that after the DEF warning comes on and the truck thinks is below a certian % level (has not be refilled) it will go into the Limp Mode. Always made me scared the sensor will go out and it will go into Limp Mode even though it is full and I have had the whole DEF system replace under warranty already.