Truck not using DEF?
Thread Starter
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Tuned
Joined: Sep 2016
Posts: 347
Likes: 12
Ha! I am such an idiot...you may be right! I always jump to think the worst, but that is certainly a possibility. Even before I took it to the dealer, the DEF gauge still showed full, but I know they don't move at the same smooth interval as a fuel tank does. It may not have gone down to the next lower sensor. Hmm....you have me thinking now. Thank you for your response.
Hotshot
Joined: Apr 2013
Posts: 10,120
Likes: 652
From: NH
wfedwar is likely right, but just for your education:
DEF is sprayed just upstream of the DPF, and it's purpose is to convert harmful nitrous oxides into harmless gases. The nitrous oxides (NOx) are harmful to the human respiratory system, among other things, in large quantities. DEF is mostly water, with some ammonia.
DEF will give your diesel exhaust a slightly sweet, bleachy smell. DEF freezes at 12F and so the tank has it's own electric heater, plus the line and the pump is heated. The truck knows...based upon temperature...when the DEF is frozen and will not attempt to inject any until sufficient time has been given for the heaters to melt the DEF. If you sniff your exhaust when temps are below 12F you will note the different smell.
These trucks have many sensors to ensure DEF injection is working properly. The level of DEF in the tank is monitored by 4 electrodes in the tank wall...not a float gauge like what is in your tank (since DEF can freeze). The distance between electrodes is only estimated. Your truck will trip a fault code if any of the DEF heaters fail, the DEF injector (dosing module) fails, or even if the DEF is old or "contaminated." There is a NOx sensor in the exhaust pipe downstream of the DEF injector. The truck knows that good DEF, being injected at the correct rate, will lower NOx to a certain level. If the NOx sensor sees high levels of NOx, it will trigger a fault. Likewise, even the NOx sensor can determine if itself is working properly.
Some people have seen strange things with the way the DEF gauge displays. Some have filled their DEF tanks but the gauge shows low. Unfortunately, this can actually cause the truck to only operate below 55mph and eventually only idle and then eventually not restart.
DEF is sprayed just upstream of the DPF, and it's purpose is to convert harmful nitrous oxides into harmless gases. The nitrous oxides (NOx) are harmful to the human respiratory system, among other things, in large quantities. DEF is mostly water, with some ammonia.
DEF will give your diesel exhaust a slightly sweet, bleachy smell. DEF freezes at 12F and so the tank has it's own electric heater, plus the line and the pump is heated. The truck knows...based upon temperature...when the DEF is frozen and will not attempt to inject any until sufficient time has been given for the heaters to melt the DEF. If you sniff your exhaust when temps are below 12F you will note the different smell.
These trucks have many sensors to ensure DEF injection is working properly. The level of DEF in the tank is monitored by 4 electrodes in the tank wall...not a float gauge like what is in your tank (since DEF can freeze). The distance between electrodes is only estimated. Your truck will trip a fault code if any of the DEF heaters fail, the DEF injector (dosing module) fails, or even if the DEF is old or "contaminated." There is a NOx sensor in the exhaust pipe downstream of the DEF injector. The truck knows that good DEF, being injected at the correct rate, will lower NOx to a certain level. If the NOx sensor sees high levels of NOx, it will trigger a fault. Likewise, even the NOx sensor can determine if itself is working properly.
Some people have seen strange things with the way the DEF gauge displays. Some have filled their DEF tanks but the gauge shows low. Unfortunately, this can actually cause the truck to only operate below 55mph and eventually only idle and then eventually not restart.
Thread Starter
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Tuned
Joined: Sep 2016
Posts: 347
Likes: 12
Troverman, great response and very informative. Thank you for taking the time to do that. It seems like if something was wrong, the truck has many opportunities to let me know. So, everything must be ok.
As far as my first refill, I saw exactly as you described. I had 50 miles remaining until 55 mph limp mode and I filled it up to full at a truck stop. Restarted it and it still showed empty, but I thought it just took time. Ended up pulling back over and it required two more start-shutdown-start cycles to finally register full again. Very weird.
On a different note, I have the DEF gauge showing full time, and on start, I see it slowly creeping back up to full, so my quantity sensors must be working properly. It certainly feels like the truck isn’t using any DEF though. 🤷🏼*♂️
As far as my first refill, I saw exactly as you described. I had 50 miles remaining until 55 mph limp mode and I filled it up to full at a truck stop. Restarted it and it still showed empty, but I thought it just took time. Ended up pulling back over and it required two more start-shutdown-start cycles to finally register full again. Very weird.
On a different note, I have the DEF gauge showing full time, and on start, I see it slowly creeping back up to full, so my quantity sensors must be working properly. It certainly feels like the truck isn’t using any DEF though. 🤷🏼*♂️
Posting Guru
Joined: Jan 2017
Posts: 1,069
Likes: 9
From: Finger Lakes, NY
Has anyone else noticed their truck sipping DEF and hardly using any at all? My first 5,000 miles I towed a 5,000 lb trailer about 1200 miles and went through an entire DEF tank. (In the total mileage) Now, I haven’t done any towing at all, I sit at 11,000 miles, and my DEF tank is still completely full from the fill up that occurred at 5,000 miles. What gives? Not that I’m necessarily complaining, but I want to make sure there’s nothing wrong. I know it doesn’t use much DEF when not towing, but it doesn’t appear to be using any! Thanks in advance for your input!
Elder User
Joined: Apr 2016
Posts: 812
Likes: 4
wfedwar is likely right, but just for your education:
DEF is sprayed just upstream of the DPF, and it's purpose is to convert harmful nitrous oxides into harmless gases. The nitrous oxides (NOx) are harmful to the human respiratory system, among other things, in large quantities. DEF is mostly water, with some ammonia.
DEF will give your diesel exhaust a slightly sweet, bleachy smell. DEF freezes at 12F and so the tank has it's own electric heater, plus the line and the pump is heated. The truck knows...based upon temperature...when the DEF is frozen and will not attempt to inject any until sufficient time has been given for the heaters to melt the DEF. If you sniff your exhaust when temps are below 12F you will note the different smell.
These trucks have many sensors to ensure DEF injection is working properly. The level of DEF in the tank is monitored by 4 electrodes in the tank wall...not a float gauge like what is in your tank (since DEF can freeze). The distance between electrodes is only estimated. Your truck will trip a fault code if any of the DEF heaters fail, the DEF injector (dosing module) fails, or even if the DEF is old or "contaminated." There is a NOx sensor in the exhaust pipe downstream of the DEF injector. The truck knows that good DEF, being injected at the correct rate, will lower NOx to a certain level. If the NOx sensor sees high levels of NOx, it will trigger a fault. Likewise, even the NOx sensor can determine if itself is working properly.
Some people have seen strange things with the way the DEF gauge displays. Some have filled their DEF tanks but the gauge shows low. Unfortunately, this can actually cause the truck to only operate below 55mph and eventually only idle and then eventually not restart.
DEF is sprayed just upstream of the DPF, and it's purpose is to convert harmful nitrous oxides into harmless gases. The nitrous oxides (NOx) are harmful to the human respiratory system, among other things, in large quantities. DEF is mostly water, with some ammonia.
DEF will give your diesel exhaust a slightly sweet, bleachy smell. DEF freezes at 12F and so the tank has it's own electric heater, plus the line and the pump is heated. The truck knows...based upon temperature...when the DEF is frozen and will not attempt to inject any until sufficient time has been given for the heaters to melt the DEF. If you sniff your exhaust when temps are below 12F you will note the different smell.
These trucks have many sensors to ensure DEF injection is working properly. The level of DEF in the tank is monitored by 4 electrodes in the tank wall...not a float gauge like what is in your tank (since DEF can freeze). The distance between electrodes is only estimated. Your truck will trip a fault code if any of the DEF heaters fail, the DEF injector (dosing module) fails, or even if the DEF is old or "contaminated." There is a NOx sensor in the exhaust pipe downstream of the DEF injector. The truck knows that good DEF, being injected at the correct rate, will lower NOx to a certain level. If the NOx sensor sees high levels of NOx, it will trigger a fault. Likewise, even the NOx sensor can determine if itself is working properly.
Some people have seen strange things with the way the DEF gauge displays. Some have filled their DEF tanks but the gauge shows low. Unfortunately, this can actually cause the truck to only operate below 55mph and eventually only idle and then eventually not restart.
New User
Joined: Apr 2017
Posts: 21
Likes: 0
From: Northern Ontario
wfedwar is likely right, but just for your education:
DEF is sprayed just upstream of the DPF, and it's purpose is to convert harmful nitrous oxides into harmless gases. The nitrous oxides (NOx) are harmful to the human respiratory system, among other things, in large quantities. DEF is mostly water, with some ammonia.
DEF will give your diesel exhaust a slightly sweet, bleachy smell. DEF freezes at 12F and so the tank has it's own electric heater, plus the line and the pump is heated. The truck knows...based upon temperature...when the DEF is frozen and will not attempt to inject any until sufficient time has been given for the heaters to melt the DEF. If you sniff your exhaust when temps are below 12F you will note the different smell.
These trucks have many sensors to ensure DEF injection is working properly. The level of DEF in the tank is monitored by 4 electrodes in the tank wall...not a float gauge like what is in your tank (since DEF can freeze). The distance between electrodes is only estimated. Your truck will trip a fault code if any of the DEF heaters fail, the DEF injector (dosing module) fails, or even if the DEF is old or "contaminated." There is a NOx sensor in the exhaust pipe downstream of the DEF injector. The truck knows that good DEF, being injected at the correct rate, will lower NOx to a certain level. If the NOx sensor sees high levels of NOx, it will trigger a fault. Likewise, even the NOx sensor can determine if itself is working properly.
Some people have seen strange things with the way the DEF gauge displays. Some have filled their DEF tanks but the gauge shows low. Unfortunately, this can actually cause the truck to only operate below 55mph and eventually only idle and then eventually not restart.
DEF is sprayed just upstream of the DPF, and it's purpose is to convert harmful nitrous oxides into harmless gases. The nitrous oxides (NOx) are harmful to the human respiratory system, among other things, in large quantities. DEF is mostly water, with some ammonia.
DEF will give your diesel exhaust a slightly sweet, bleachy smell. DEF freezes at 12F and so the tank has it's own electric heater, plus the line and the pump is heated. The truck knows...based upon temperature...when the DEF is frozen and will not attempt to inject any until sufficient time has been given for the heaters to melt the DEF. If you sniff your exhaust when temps are below 12F you will note the different smell.
These trucks have many sensors to ensure DEF injection is working properly. The level of DEF in the tank is monitored by 4 electrodes in the tank wall...not a float gauge like what is in your tank (since DEF can freeze). The distance between electrodes is only estimated. Your truck will trip a fault code if any of the DEF heaters fail, the DEF injector (dosing module) fails, or even if the DEF is old or "contaminated." There is a NOx sensor in the exhaust pipe downstream of the DEF injector. The truck knows that good DEF, being injected at the correct rate, will lower NOx to a certain level. If the NOx sensor sees high levels of NOx, it will trigger a fault. Likewise, even the NOx sensor can determine if itself is working properly.
Some people have seen strange things with the way the DEF gauge displays. Some have filled their DEF tanks but the gauge shows low. Unfortunately, this can actually cause the truck to only operate below 55mph and eventually only idle and then eventually not restart.
I am having the total opposite as to what the OP had posted. On the 4th of December my low DEF fluid message popped up, said I had 800 km(500 miles) until empty. On Forscan it showed 10% left. I usually put a jug in, 2.5 gallons, when the light comes on, I'm sure I could squeeze two in but don't want to overfill it and have it leak out onto the paint. Found DEF fluid at the pump for 0.89/liter when I was in town visiting my parents so topped it up, put in about 23 bucks worth so about 25 liters give or take.
My DEF gauge didn't move on the display or forscan. I drove back to my parents house, maybe about 5-6 miles and it didn't move. Next day still showing low. I reset the Fuel History on the display(it was set for the last 30 minutes) and soon as I did that both the display and forscan showed 100%.
Had about 19800 km on the odometer, I use my 1st trip meter to see average fuel consumption and reset it every 10000 km. Reset it at 19900 and now have 20680 km on it. I have had two regens since then, one basically as soon as I reset it and another one yesterday. DEF fluid on the display is only showing a quarter left and forscan shows 23.53% left. All my driving has been empty except for about 100 km where I had my enclosed 8.5 x 12 sled trailer with one snowmachine in it.
It's been cold for the past 4-5 days, -15C to -20C, forscan shows DEF fluid at -11C. Unsure if the cold is making the gauge act up or if I have actually used 3/4 of a tank of DEF in the last 9 days/880km. First diesel so don't know if I would use more during the winter months??
Truck is in the garage at work right now warming up so will check it tomorrow to see if the DEF gauge goes back to normal or not. I'm heading to see the parents on Christmas and will be filling the DEF up at the pump again and will see how many liters/gallons goes back in to see if it's the gauge not working properly, or if I'm using more DEF for some reason or another.
Hotshot
Joined: Apr 2013
Posts: 10,120
Likes: 652
From: NH
On pickups, the DEF is injected upstream. On chassis cabs, the SCR is located after the DPF and thus DEF is injected downstream. Seems strange Ford chose to do it this way, but that's the way it is.
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New User
Joined: Apr 2017
Posts: 21
Likes: 0
From: Northern Ontario
Well, after the truck sat in the garage warming up for about 10 hrs, the DEF gauge started working right again.
It slowly crept up(took 20 minutes) to register back to full on the gauge, and it registered 100% on forscan, event though I had two regens. I had filled it right up thought so maybe the extra DEF fluid in the filler pipe might contribute to it still showing full?
So now that's it showing full, and will definitely freeze again being it's winter now up here, is this something that could possibly keep our DEF gauge showing full(or low if the DEF freezes at lower mark)?
It slowly crept up(took 20 minutes) to register back to full on the gauge, and it registered 100% on forscan, event though I had two regens. I had filled it right up thought so maybe the extra DEF fluid in the filler pipe might contribute to it still showing full?
So now that's it showing full, and will definitely freeze again being it's winter now up here, is this something that could possibly keep our DEF gauge showing full(or low if the DEF freezes at lower mark)?
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