DEF Contamination

Just got the Check Engine+DEF light. Owners manual says to drain and clean tank. I get the drain part, but how do you "clean" the tank. I think I found the tank and the hose. Any idea how to "release" this hose clamp without damaging it? It is not one that uses a screwdriver to loosen and tighten. Looks like it has little tabs that fit into the holes like a belt. Is DEF supposed to be clear? Thanks.

I can only answer your last question, as I dumped in my first 2.5 gallon container of DEF. It was clear.

Sailordive,
What page in your manual suggests that you "drain and clean out your DEF Tank"?
The CEL and DEF/SCR could just be empty.
Have you refilled it with fresh clear DEF fluid?
Suggest you try your nearest Tractor Supply store.
They have the TerraCair Ultra Pure DEF fluid for ~$11.00 for a 2.5 gallon kit with
the flex spout.
I would NOT touch the SCR/DEF system if your Sprinter is still with in the Emissions
Warranty (100k miles).
Take it an authorized Mercedes Benz or Freightliner Sprinter dealer and have the SCR/DEF issue
repaired under your 100k emissions warranty.
Yes, DEF Fluid is completely clear.
Has someone put some other fluid in your DEF tank?
If so, go back to them and have them pay for any repairs/draining/cleaning that an
Authorized MB/FL dealer (find a commercial Sprinter dealer with the Sprinter Specific
high bay/heavy duty shop area if you can) recommends to fix your SCR/DEF.
OBTW SCR is the abbreviation for Selective Catalyst Reduction and DEF is the abbreviation for
Diesel Exhaust Fluid.
*************************
Diesel exhaust fluid is a mixture of synthetic, high-purity, automotive-grade urea and deionized water. This liquid is clear, nontoxic, nonflammable, non-explosive, and generally nonhazardous. Additionally, DEF is classified as a minimum risk for transportation. The fluid is mixed at a ratio of 32.5 percent formaldehyde-free low biuret urea and 67.5 percent deionized water. Heavier than diesel, exhaust fluid weighs 9.1 pounds per gallon, and while it will freeze at 12 degrees, its composition and quality are not affected by freeze or thaw.
! teaspoon of salt (NACL) will pollute 5000 gallons of DEF Fluid and render it useless.
That's why I try to use the Terracair Ultra Pure DEF whenever possible.
Hope this helps,
Roger

It seems that, at least is some cases, the CEL and the DEF message appearing together are due to one or both of the NOx sensors having gone bad. Take it to a reputable repair station and have that possibility checked out.

Sailquick Pg 195 of the Owners Manual. I have tried to upload the photo. Not sure that will work. We are the only ones that touch our DEF tank. 3x the DEF fills have been from the Adblue DEF 2.5 gallons from Walmart (new containers are used each time). We never have left overs. The other times, we get the DEF at the pumps at Pilot or Flying J's truck stop. The last fill was at a flying J, more than 1250 miles ago. We have already had one NOX sensor go bad (last May). As I recall, I got the Check Engine light (as well as a big engine shudder) but I do not recall getting the DEF warning at the same time. We also had computer issue in the 1st 30k miles that caused a DEF warning and a start countdown even after filling the tank. That just required a computer update. Interestingly, I rolled to 100K, just as the warnings went off. Luckily, I have the extended warranty so if it would have been covered under the emission warranty, it still should be covered.

I got the same warning last year. I could not believe that the DEF had gone bad just sitting in my tank for a couple months so I cleared the fault code with my Ultragauge and topped off with about 1.5 gallons of new DEF. Six months and about 5000 miles later the message has not returned. There have been posts here about the DEF sensors being affected by crystal formation when exposed to air when the tank is partially full, so I'm going with that explanation and I no longer let the DEF stay low when not in use.