[hypoxia]

This is the best service instruction manual I have found for the early 2010-2017 Def Tank and Head.  Great photos and detailed instructions.
I had a DEF quantity gauge that went from over half full to nearly empty causing a code.  If it would have gone to empty I would have been limited to 5 MPH from what I understand.  Of course it had to happen in Mexico.  I plan to pull the DEF Head out, flush/clean the tank and head unit, replace the suction filter on the head unit and see if there is any visible problem.  The DEF level sensor is replacible and there are testing procedures in the manual.
It is a great time to remove some of the hardware, bead blast & paint it.  DEF is corrosive and some has likely spilled in its lifetime.  I'm using POR15 as my paint, that stuff is bullet proof.

[Richard]

Amen on POR. Got some on me two weeks ago, and there is still a wee bit.

This is a trick told to me at the car paint shop I use. Put a plastic grocery bag between the lid and can if you have some left. It works. Otherwise the lid welds to the can never to open again.

[hypoxia]

Amen on POR.  Got some on me two weeks ago, and there is still a wee bit.

This is a trick told to me at the car paint shop I use. Put a plastic grocery bag between the lid and can if you have some left. It works. Otherwise the lid welds to the can never to open again.

Yes, I use zip lock bags but grocery bags are thinner and may work better.  I'll stop at the paint store today and get a couple of empty pint cans to use.  They take a beating making sure to get the lid on tight after a few openings.  I've learned to be careful not to get any on me or anything else, it will be part of you for a while.

[hypoxia]

I drained the DEF tank (1/4" Allen Wrench), unplugged the electrical connectors and DEF hoses, removed & plugged coolant hoses.  There are two straps holding the tank in place, I cut those and removed the tank.  There are two small 1/8" Hex head fasteners that hold the DEF Head in place with a metal ring.  I removed the ring and pried the DEF Head up using flat screwdrivers and removed it.  It is held in place with an "O" ring.  There was a lot of dirt & grit in that recess above the "O" ring and some fell into the tank which had to be cleaned regardless.  The tank & DEF Head were spotless, no crystalized DEF or anything.  I pulled the Level/Temperature Sensor 960-0111-12 off & looked for a replacement, no joy.


I went back & looked up the fault code I had in Mexico, it was 3497 Aftertreatment 1 Diesel Exhaust Fluid Tank Level-Data Valid but Below Normal Operating Range.  I then read the Cummins Service Notes when they replaced the SCR 3 weeks earlier.  


Technicians notes  "I WANT TO EMPHASIZE DURING THIS REPAIR THERE WAS ZERO ACCESS TO ELECTRICAL SENSOR JUNCTION CONNECTOR AS IT WAS LOCATED ON TOP OF SCR.  TIGHTLY BOXED IN WITH WELDED PANNELS.  I HAD TO REMOVE SCR MOUNTING BRACKETS WITH TWO TOTAL AND USED A TRANS JACK TO LOWER SLIGHTLY BEING CAREFUL NOT TO RIP CHASSIS HARNESS I HAD TO USE A LONG PICK AND ANGLED LONG NEEDLE NOSE TO RELEASE LOCKS AND DISCONNECT ALL ELECTRICAL CONNECTORS BEFORE FINALLY LOWERING THE REST TO THE WAY. TO RE-INSTALL I USED THE SAME METHOD IN REVERSE."

Then I read the Level Sensor Testing Instructions "The Level Sensor must be tested while in the vehicle wiring, while the vehicle is running, because the Dosing Unit completes the output circuit of the Level Sensor. A simple volt meter across the yellow and black leads will correlate to the DEF’s level, while a volt meter across the red and black leads will correlate to the voltage being supplied to the unit"

I came to the conclusion that the most suspect item is the wiring that the tech had so much trouble with and probably not the sending unit.  More to come.....