Help! Advice on DEF

[KatanaPilot]

Originally Posted by richhop25

My experience was an $8,000 lesson worth noting here. Mine is a 2014 chassis. The owner's manual states that when the light comes on to add DEF within 1,000 miles. That was my practice - I followed the manual. Discovered that a far better practice is to refill every 2,000 miles. Reason? DEF tank has a heating element, a pump, and downstream sprayer, sensors and particulate filter. All of which had to be replaced due to my waiting for the DEF light to come on.
You can wait, but it might just cost you a bundle some day. I prefer to add 2.5 gallons every two thousand miles and not have the big problem. Sprinters develop enough problems without me adding to the list.

My understanding of the system was that eventually the display would go to countdown mode (indicating how many starts you could perform before limp mode) and it was not possible to damage the DEF system per se.


Could you please explain how waiting until the fluid level got low damaged your DEF system to the point of needing a complete replacement? And why was it not covered under the 8 year emissions warranty?

[MNtraveler]

Originally Posted by AudiDudi

Doesn't the DEF level display on the dash when you cycle through the maintenance items? It looks just like the fuel level display. It also show how many miles to the next service/oil change.

Please tell us what button sequence you follow to get to the DEF gauge. Thanks.

[MNtraveler]

Originally Posted by Gonefishing1

May not have a gage. But if you cycle through your display it should show how many miles before the def needs some added.

Please tell us what button sequence you follow to get to the DEF due mileage indicator. Thanks.

[vettecrazy]

We have friends with big A Diesels that don’t have to add DEF, yes it’s in the manual now that we know what to look for. They didn’t explain that we needed to add that when purchasing, being new to a diesel this was foreign to us. We know it now and the Service Mgr got mad when he found out our salesman never explained that. We are fine.

[AudiDudi]

Originally Posted by MNtraveler

Please tell us what button sequence you follow to get to the DEF due mileage indicator. Thanks.

Ignition in position 2, immediately press the M button 3 times. Works on my 2016 Prism 24G

[oregonct]

I usually keep a 2.5 gallon in storage in my Sprinter just in case. I fill it up very 1500 miles just to make sure the light doesn't go on .. I probably am OCD :-)

[JimHs1]

Originally Posted by MNtraveler

Please tell us what button sequence you follow to get to the DEF due mileage indicator. Thanks.

My MBS has the steering wheel buttons. When started the driver display shows the odometer. From there I push the right button once and then the up arrow 4 times. It shows a gauge of how much is left. No "mileage indicator". Im still exploring what's there.

[Mikegjax]

BTW, DEF countdown mode is 16 starts or 500 miles. I like to top mine off before each trip. Not required by any means, but just how I do things. Do what ever makes you feel comfortable.

[MNtraveler]

Originally Posted by AudiDudi

Ignition in position 2, immediately press the M button 3 times. Works on my 2016 Prism 24G

Thanks - gonna give it a try!

[MNtraveler]

Originally Posted by JimHs1

My MBS has the steering wheel buttons. When started the driver display shows the odometer. From there I push the right button once and then the up arrow 4 times. It shows a gauge of how much is left. No "mileage indicator". Im still exploring what's there.

Thanks! That won't work for me but may help others.

[rflarouere]

We have a 2015 Forest River Solera (our first RV and first diesel). On one of our first trips, the idiot light came on so we pulled over and called Good Sam Road Assist. When I described our situation, the tech on line diagnosed needing DEF ! He told us that it was ok to drive to a WalMart within 10 miles. We added DEF and had no problem after that. NOW, we always have a 2 1/2 gallon DEF in the basement.

[MNtraveler]

Is this the DEF gauge other are seeing? This is inside our onboard computer screens. It’s certainly not the gas gauge since the tank is full. I have no idea what the entries mean other than “zero hours.” (The small icon is an indicator that the fuel fill port is on the left side.)

(If you turn the ignition to position 2 and press M repeatedly, it cycles through the trip odometer and clock to the oil level monitor gauge which takes a moment to get a level reading. That is not a DEF gauge.)

[AudiDudi]

Originally Posted by MNtraveler

Is this the DEF gauge other are seeing? This is inside our onboard computer screens. It’s certainly not the gas gauge since the tank is full. I have no idea what the entries mean other than “zero hours.” (The small icon is an indicator that the fuel fill port is on the left side.)

(If you turn the ignition to position 2 and press M repeatedly, it cycles through the trip odometer and clock to the oil level monitor gauge which takes a moment to get a level reading. That is not a DEF gauge.)

Attachment 198466

I'll try to get a pic tomorrow and post it. I was at 40% DEF and added 2.5 gals and it brought it up to 90%. About 4000 miles since last add and it was at 80% then.

[AudiDudi]

Originally Posted by MNtraveler

<snip>

(If you turn the ignition to position 2 and press M repeatedly, it cycles through the trip odometer and clock to the oil level monitor gauge which takes a moment to get a level reading. That is not a DEF gauge.)

Attachment 198466

Here's what I get when I have the ignition in position 2 and *immediately* press the M button 3 times. I think you need to press M with 2 seconds of turning on the ignition.

[Mikegjax]

If you read your MB or owner's manual for the correct model year, it will tell you exactly how to check your DEF level. Some model years only have the DEF light.

[marvmool]

We have a 2018 Sunseeker MBS... One of the menu items in the center of the message panel has a DEF level indicator. I usually add DEF when down around 50%... usually get about 1000 miles or so before that happens.

[AudiDudi]

Originally Posted by marvmool

We have a 2018 Sunseeker MBS... One of the menu items in the center of the message panel has a DEF level indicator. I usually add DEF when down around 50%... usually get about 1000 miles or so before that happens.

What kind of fuel economy are you seeing? Do you know how big your DEF tank is? 1000 miles to go through 1/2 a tank seems like a lot to me.



My 2016 Prism has a 4.5 gal tank and I am seeing 14+ or so mpg typically when towing a Sonic on a dolly. My last DEF add was 2.5 gals and I had gone about 4000 miles. That brought the DEF tank from 40% to 90%.

[FFred]

The DEF dries out in the tank and can cause the check engine light to come on.


To me its vastly simpler to go and fill the tank fairly often than to create my own problems.