DEF Issues

[dedmiston]

I drove a RAM 2500 diesel for 12 years until I upgraded to a pre-owned 2014 3500 diesel earlier this year. I knew nothing about DEF when I bought the "new" truck in March. My first introduction to DEF was when I saw the extra gauge on the dash and the filler inside the gas cap door. Well whadda ya know? I caught on quickly enough and filled the DEF tank as needed.

Fast forward to last week...

We left on a trip last week to go white water rafting up on the American River up in the gold country. I noticed before we left that the DEF level was just below 3/4 and didn't give it much more thought. Off we went.

Coming down the back side of the Grapevine I noticed that the check engine light was on and the DEF gauge showed it was empty. Oh no. I stopped at the next gas station and bought a few jugs of DEF to refill. By then a message popped up and told me "5MPH Max Speed in 150 mi. Service DEF System. See Dealer."

Swell.

I managed to get about three gallons of DEF into the tank before it overflowed. The needle stuck at Empty though.

So we limped to Bakersfield and spent the night at an RV park down the street from the Dodge dealer. The next morning the folks at the Dodge dealer took four hours to check it out and declared that everything was just fine and the message was bogus. They reset the errors and sent me on my way.

We had about five hours to go from there. About an hour away I noticed that the needle was down to 3/4 tank. That was fast. I tried to add more when we stopped for fuel, but the tank was full and I couldn't fill it any more.

Over the next few hours the needle fell quickly until it finally got past the red again and gave us a similar message: "Speed Limited to 5MPH in 200 mi. Refill DEF."

Luckily our destination was only about 20 miles away, so we got to camp and sent in to the closest dealer the next morning for service. They diagnosed it and said that the DEF pump was faulty. They replaced the pump and the sensor (part of the pump).

The service writer there was much more knowledgeable than the one in Bakersfield. She said that the sensors aren't mechanical, they're sonar. The sonar sensors run into trouble if you refill the DEF too soon.

"DEF level sensors operate off a sonar sensor and must see an air gap before level will actually drop. Filling the tank before it reaches the 1/2 way mark, we have seen issues with it detecting incorrectly and can set a fault in system. To prevent this we just recommend not filling the tank unless it is between the 1/4 and 1/2 mark. The only other thing that I can think of that might really help and prevent possible issues is to ALWAYS use your exhaust brake. Make it a habit to turn it on as soon as you get into the vehicle. This will help to reduce carbon build up in the exhaust brake and keep it working properly... saves your brakes."

I thought I'd check here and see if this jives with everyone's understanding. And if so, are there other things I should keep in mind with the newer diesel?

I also noticed on this trip that almost all of the gas stations along I-5 and I-99 sold biodiesel instead of good old #2 diesel. Is this kosher? Anything I should be concerned about?

[Me_Again]

I wish one could default the exhaust brake to be on all the time. When towing it restarts in Tow/Haul but not exhaust brake.

DEF usage is related to the amount of fuel used. So when towing heavy it uses a lot more DEF. I wait until it is below 1/2 about an 1/8 of an inch and then put a box of Peak Blue DEF in from WM. The pre DEF 6.7 had a lot more trouble with the turbo exhaust brake not sliding back and forth.

[dedmiston]

Interesting consensus from all of you on the exhaust brake. I use it whenever I tow, but rarely use it otherwise. It seems like the exhaust brake scrubs off enough momentum on the downhills to negatively impact fuel economy. Maybe that's in my head though.

What about DEF usage when towing vs. not towing? I don't really notice the gauge drop very much, but it seems to drop quicker when I'm towing. I can't tell if that's real or if it's just in my head.

[IdaD]

I've never heard that before but thanks for posting so the rest of us can benefit. I generally let my DEF run down pretty low before I refill and I'll continue that going forward. I know sales guys are generally worthless but one of the things the salesman told me when I bought it was to run the exhaust brake as much as possible and I've done that, so that seems to be a common bit of advice.

[DutchmenSport]

First, glad you finally got some good help and advise, although you must have had your serious concerns initially. At least now you know what to expect and how to handle it in the future.

Second, I was originally concerned about bio-diesel, but (in my Chevy), it's never caused any problems. From what I've read about diesel engines, they can run on chicken fat and French Fry grease! So, bio-diesel is a non-issue.

I don't have experience with Ram's, but in my Chevy, I don't have a gauge. I just get a warning notice, something like, Fill DEF in the next 750 miles. Then it goes away and pop-up again later with a lower mileage. I've not had problems filling before filling when that message comes up. And it seems, the more I'm using the truck, the less DEF it's actually taking. Seems my first fill up was right at 2000 miles, then 4000 miles, then 6000 miles, now it seems to be not empty and no warnings between oil changes (about 8000 miles), really weird, but I'm not complaining.

I think good old #2 diesel is still used for home heating, and the diesel at the pumps is a lot cleaner burning now.

And you are right using your exhaust brake. I love mine! I don't use it not towing as I drive on flat roads most of the time. But when traveling with trailer in tow, it's absolutely marvelous!

If cruise control is set, with diesel exhaust, and tow mode, you can tow with those 3500's through the mountains, and pretty much touch nothing but the steering wheel. It's really a sweet ride!

Good luck with your new truck! Gotta love those 3500's, there's nothing like them in the diesel world!

[BB_TX]

Ford sensors may be different, but I have never experienced anything like that. And I have refilled the DEF tank at various levels including over half full if I were getting ready to leave on a long trip.

[azrving]

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