No DEF warning light

I’m fairly new to the Bluetec engine although not to the forum. I did a search for my query and read a pile of threads but didn’t find anyone with my problem. There a bunch of posts about DEF warning lights and CEL’s but I didn’t find any posts on a lack of the warning light. Quite possible I missed it as the search engine doesn’t always get me where I wanna go.

Anyhow, I have a 2011 Winnebago view on a 3500 chassis with 45k miles on it. Had it serviced last Fall and the shop refilled the DEF then but I haven’t had a low DEF warning light since, and haven’t since I’ve owned the rig. I did my homework before I bought the rig and know the typical refill intervals.

So my question is...if there is a problem in my system(and I’m sure there is!) and I’m not getting the 10 start warnings what are the implications? Am I damaging the engine in any way if my DEF has run dry or is the effect that I’m polluting more than I should but the engine is ok?

Thanks for any help.

If you are running without DEF, you are polluting more than the vehicle is supposed to. The engine is not affected. There will be more NOx coming out of your tailpipe.

However, MB has worked very hard, at the direction the EPA, to make it impossible to run far without DEF.

Perhaps you should fill your own DEF tank and see how much it takes.

Any noticeable performance issues?

so how many miles since the shop filled the DEF?

What makes you think there is a problem?


- - Mike
2012 Sprinter 3500 Extended converted B-Van by Airstream

Bobnoxious said:

Any noticeable performance issues?

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Not that I’ve noticed. Power is solid, mpg unchanged.

mikeme said:

so how many miles since the shop filled the DEF?

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I meant to include that key piece of info. At least 10k almost all highway miles. Thanks for the reminder.

The Sprinter forum consensus is keep the DEF topped-off and avoid DEF warning light activation.

Is there a video posted somewhere that demonstrates the process of topping off the DEF?

Your cab chassis may have the large DEF tank which I recall is around 5.8 Gallons. It's possible you just haven't run it down yet, but you will pretty soon. Consensus thinking is pretty much to keep it topped off.

I'm not remembering with great accuracy but I have added maybe 7.5 gallons over the course of 18,000 miles and the dealer did a partial fill in there as well.

Mike DZ said:

If you are running without DEF, you are polluting more than the vehicle is supposed to. The engine is not affected. There will be more NOx coming out of your tailpipe.

However, MB has worked very hard, at the direction the EPA, to make it impossible to run far without DEF.

Perhaps you should fill your own DEF tank and see how much it takes.

Click to expand...

Thanks Mike. I would assume I might fail inspection then but I’m glad the engine is safe at least.

WanderOften said:

Thanks Mike. I would assume I might fail inspection then but I’m glad the engine is safe at least.

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Unless you bought it used and it was modified some fashion, I believe you have the large tank and just haven’t hit the warning yet. 3k highway miles per gallon is not out of the realm of possibility.
Why don’t you just fill the tank pro-actively instead of risking problems?

Sdavis said:

Is there a video posted somewhere that demonstrates the process of topping off the DEF?

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Sure, you tube has a number of them, some use a funnel, others use the plastic hose that comes with the 2.5 gallon box, others use the 1/2 gallon ADBlue special bottle, and still others use the DEF pumps at the big boy diesel pumps at a truck stop. In all cases you have to locate your DEF fill (blue or black cap with the letters DEF on it) unscrew and insert your fill device of choice (note above), fill until full, bump the vehicle to burp and fill again. NOTE: Flush any over flow or spill immediately with plain water, DEF will dry to a white crust and is corrosive as it is a urea solution.

Sdavis said:

Is there a video posted somewhere that demonstrates the process of topping off the DEF?

Click to expand...

I purchased two of these 1/2 gallon bottles and refil them from larger 2-1/2 gallon cantainers. I found it cumbersome and difficult to hoist a 20-pound box, while manipulating a Water Wiggle spout without spillage. I am reluctant to buy DEF at pump because of contamination concerns.

https://m.youtube.com/watch?v=3_W9NM2VZOs

rollerbearing said:

Your cab chassis may have the large DEF tank which I recall is around 5.8 Gallons. It's possible you just haven't run it down yet, but you will pretty soon. Consensus thinking is pretty much to keep it topped off.

I'm not remembering with great accuracy but I have added maybe 7.5 gallons over the course of 18,000 miles and the dealer did a partial fill in there as well.

Click to expand...

Winner, winner chicken dinner! As luck would have it the low DEF light went on today coincidentally so it looks like you were right. Thanks for the help.

Sprinter owners manual has details about DEF.

My 2013 manual says “For
this reason, refill the DEF tank regularly
during vehicle operation, or, at the latest,
after the first warning message has been
received from the on-board computer.”

The manual also says “If the DEF supply drops below
1.5 US gal (5.5 l), you receive the first warning
message and you hear a warning tone. After
the first message appears, the remaining DEF
supply suffices for approximately 1000 miles
(1600 km) in normal driving conditions.
Then, the reserve range of 0.8 US gal (3.0 l)
is reached. Once the reserve range has been
reached, you receive the next warning
message and you hear a series of warning
tones. After the first message appears, the
DEF reserve suffices for approximately
1200 miles (1900 km). You can, however,
only start the engine another 16 times.”

Knit said:

Sprinter owners manual has details about DEF.

My 2013 manual says “For
this reason, refill the DEF tank regularly
during vehicle operation, or, at the latest,
after the first warning message has been
received from the on-board computer.”

The manual also says “If the DEF supply drops below
1.5 US gal (5.5 l), you receive the first warning
message and you hear a warning tone. After
the first message appears, the remaining DEF
supply suffices for approximately 1000 miles
(1600 km) in normal driving conditions.
Then, the reserve range of 0.8 US gal (3.0 l)
is reached. Once the reserve range has been
reached, you receive the next warning
message and you hear a series of warning
tones. After the first message appears, the
DEF reserve suffices for approximately
1200 miles (1900 km). You can, however,
only start the engine another 16 times.”

Click to expand...

It does say that (in the "Introduction" section), but the last sentence incorrect -- I assume a translation garble. It is not true that you get the "16 starts" after the "first message" as stated.

The correct behavior is described on page 178 (and several other places):

If the supply of DEF is less than 1.5 US gal (5.5 l), the Check Diesel Exhaust Fluid See Operator's Manual message is shown in the display.
If the supply of DEF falls below the reserve range of 0.8 US gal (3.0 l), the xx starts remaining message is displayed. In the display, xx corresponds to the number of possible remaining engine starts (16 to 0).

This omits the erroneous "16 starts after first message" statement.

Also, N.B., that you don't actually always get 16 starts. I have only seen 10, and others have reported the same.

I have been wondering... do you just top up the DEF fluid up to the fill cap. I have looked for a level indicator in the reservoir, but I see nothing.

I saw someone mention that they do top it up and give it a bump to burp it and add some more. Is that the general consensus? I don't want to have to think about it, I just want to go out once a month and top the thing up as full as I can and forget about it until the next month...

I fill mine right to the top of the filler neck... then check it again some time later; often it will drop a bit more, so I add more.

To avoid unnecessary wallet flushes, top-off DEF every other diesel fueling.