Low def light on but tank is full

Do a manual regeneration clean it up. Then it has to pass a DEF fluid quality test. If you can keep driving it, the ECM will run the tests and either clear the message or turn the light back on. It has to see the system working normal for the message to clear. I have a 2015.5 Chevy 3500 single rear wheels.

Low def light on but tank is full. There is one for DEF level indication stuck on full requiring a PCM recalibration. The fact that you hit some bumps and the level went back to full suggests a possible bad electrical connection or something in the DEF tank covering the sensor. I have heard of the DEF heater belts dislodging and possibly covering the sensor.

145000. Hello this could be caused by a failing def level sensor within the def tank. Another cause would be the engine needs a ECM calibration update from the dealer. Ok, thanks. I drove it 190 miles from the dealer, and I know we so in your professional opinion. The level sensor is known to be an issue.

When it lit the amber outline check eng light and the “Low DEF!” message appeared again, I topped off the tank (4.5 gal.) and the Low DEF message on the LCD cleared. I attributed this to cold temps and the lines maybe freezing since the DEF I added was warm (70* or so) and it cleared quickly. The DEF tank is full, or at least it's acting full. Yet the light is still on and I'm down to "250 miles until no start". The closest VW dealership to me is at least 300 miles away, I'm planning on going there in a couple of weeks but I'm scared the car is going to leave me stranded!To reset the DEF light, follow these steps: Turn the ignition on. Press and hold the "0" button until you hear a beep sound. Press the "M" button until the screen displays "Reset 51." Press and hold the "0" button until the screen says that the reset is done. Turn the key on.If the DEF tank was low when you started, you will likely get Low DEF light on the dash after tuned, to avoid this make sure the DEF tank is at least 1/4 full. On 17-19 model years make sure the soot levels are below 70%, if soot levels are above 70% you will need to do a force regen before tuning.******Mar 4, 2021 · Ok I’m at the mechanic now his telling me I should replace my whole system but I don’t think that’s the issue It’s saying code 3712 but my truck is saying low level of def. On your issue. If the def level is reading low and the tank is full I would check the wiring by the pdm. If there is no issues present then I would replace the QLS ... The fuel tank pressure sensor measures the positive and negative pressure in the fuel tank. This sensor also monitors the vapors in the engine.The information gathered is sent to t...

Jun 8, 2022 · The def tank utilizes electronic resistance sensor. depending on the temp/humidity where you live, def crystallizes on the sensor and shows as if the tank is full/half, even though the actual level is lower. Eventually the crystal melts and all of a sudden you see a significant drop in the bars. Best is to track the mileage and add accordingly. Mar 19, 2015 · Low-Empty DEF notifications. When I got the 2014 truck new in Dec of '13, I ran the first tank of DEF way down just to make sure I knew & understood how far I could go by watching the "Low DEF" messages pop up, indicating how far I could go before my speed was limited to "5 mph". Coming back from Ohio with a (new box in the back seat), I ... Then I got a CEL for about 30 min and then directly to the “10 starts remaining” light. I didn’t get a DEF low warning light, just straight to the "10 starts remaining" light. At the next stop I bought some DEF and when I filled the DEF tank it was only a gallon low, no where near being empty.And when the DEF level has gone far too low, it will prevent the engine from starting unless you have added the right amount of fluid. Driving With A DEF Light Turned On. Before the tank runs empty, there is an alert on the dashboard that comes on, which is the DEF light. But if the DEF goes below 2.5 percent, the light will turn solid amber ...I believe its 5.2 Gallons, somewhere in that range. I've never been able to add more than about 2.5 Gallons when the low DEF light turns on. Once I finish adding DEF until it is "Full" the light goes away and then a day or two later it comes back on, I top it off, and the light goes away until it is actually time to fill it up again.Hi there. I have a 2017 Amarok V6. A few days ago a yellow warning sign starter to appear on the dashboard. Even after the full refill of the ad blue tank, the message keep staying with the km counter getting lower by days.

PDI Big Boss CAT 3406E/C15/C16 Low Mount Exhaust Manifold. $1,895.00 Unit price / Unavailable. Choose options Choose options View details. PDI Diesel. PDI Big Boss CAT C15 Acert Exhaust Manifold. $1,895.00 Unit price / Unavailable. Choose options Choose options View details. PDI Diesel.1. The truck does not need fuel injector cleaning at such low miles (17K). In fact they don't recommend it. 2. As long as the Def is API approved and run it and keep the tank full but don't overfill it. Don't open the fuel spout unless you have to, because adding air to the tank can degrade it.DEF gauge and indicator light or LED flashing on the gauge default to "E" is an standard for an active SCR related fault. Not necessarily a defect with the DEF level gauge itself or that the DEF is low. Need to hook up, could be many things.Then in 2017, last winter, The DEF heater in the tank failed and it immediately went into "Slow" mode. Dealer replaced it under warranty and all was well. Now in 2018 with 110,000 miles, the light came on when in fact I had 3.5 gallons in the 5 gallon tank. The light went off and no problem since.

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First oil change at 9800 miles, required 2.75 gallons DEF to refill tank using VW filler bottle for the first 1/2 gallon, twisting off the plunger top, and refilling the VW bottle from the bulk 2.5 gallons I got at NAPA for $10.50.Are you running out of CO2 for your tank and need to find a refill location nearby? Don’t worry, we’ve got you covered. In this article, we will guide you through the process of fi...The Polestar 4 comes with a bold design choice to completely remove the rear-view window. Drivers will rely on a camera alone for reversing. Polestar introduced the Polestar 4, the...A check engine light is one of the most common reasons for car owners to visit the mechanic. The light may be on because there is a problem with the vehicle’s emissions system, fuel system, or a sensor. The most common reason for the check engine light to be on is a gas tank issue. The main causes are air in the fuel line or a clogged …Icelandair just added a new Economy Light class to compete better with low cost airlines WOW Air and Norwegian Air. Checked bag fees are extra. By clicking "TRY IT", I agree to rec...

Apr 4, 2019 ... In this video I preform a DEF Level reset on this 2011 GMC. This is a fairly common issue on these trucks and a pretty easy fix. -Enjoy!Do you know how to make a paper tank? Find out how to make a paper tank in this article from HowStuffWorks. Advertisement Origami is the Japanese art of folding paper to make model...Generally, a warning light will come on when DEF needs to be added soon. If the light is ignored for too long, the vehicle will likely go into a reduced power mode. If the DEF level falls too low, the engine will not start until fluid is added. To avoid getting stranded, make sure you understand how your particular car or truck is designed to ...Thinking that the dealer did not fill the DEF tank before delivery, I took the truck into the dealer. The dealer tried to add DEF, and the tank immediately overflowed. Thus, we verified that the tank was physically full at, or above 100 percent. The dealer then connected his OBD II reader and got the same result; 45 percent full.It only happens when traveling a longer distance continuously and both times it was colder ambient temperature and at >6000ft above sea level (snowboarding in Flagstaff). Once it reset on its own after a few restarts. Once I used an OBDII scanner to clear code and it didn't come back. Both times DEF tank has been at least >50% full.Diesel Exhaust Fluid is a mixture of urea and water. Basically the same ingredients as urine. But don’t try peeing into the DEF tank to refill it – DEF is a specific proportion (32.5% urea, 67.5% water) and pretty pure. The impurities in your pee would mess up the SCR catalyst. Urea is nasty stuff – it’s corrosive and will eat through ...Springfield, VA. TDI. ‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e. Nov 24, 2014. #4. The DEF tank uses a three-position level sensor (four electronic probes). Add a few liters of fluid, then turn the ignition on for 30 seconds. The system will reset the low fluid alarm if enough fluid has been added to satisfy the sensor.The sensor positions are (paraphrasing) empty, low, and okay.The countdown is triggered at the low level, and reset at the okay level. If the vehicle ends up consuming more AdBlue than calculated and triggers the empty level sensor, a different, more urgent message is displayed on the cluster and engine start will be prohibited. …How many miles do you get on a full tank of DEF? ... What is especially odd is that I got a low light less than 1000 miles ago and added on bottle (purchased at the dealership). The message went away for a few weeks until just recently. I went last night and purchased another 2 bottles. After filling up, I did the 3 start/run for 30 ...This answer was rated: ★★★★★. I have a 2016 freightliner HDJE6489 the def tank is full but…Ok I’m at the mechanic now his telling me I should replace my whole system but I don’t think that’s the issue It’s saying code 3712 but my truck is saying low level of def. On your issue. If the def level is reading low and the tank is full I would check the wiring by the pdm. If there is no issues present then I would replace the QLS ...Motor Mav. 2.22K subscribers. Subscribed. Like. 38K views 1 year ago. Hi, why DEF light blinking on Freightliner tank is full? Though the DEF light blinks mainly when the DEF tank...

When it lit the amber outline check eng light and the “Low DEF!” message appeared again, I topped off the tank (4.5 gal.) and the Low DEF message on the LCD cleared. I attributed this to cold temps and the lines maybe freezing since the DEF I added was warm (70* or so) and it cleared quickly.

Any of these mistakes could cause the DEF gauge to read empty. You should always leave a third of the DEF tank empty. Read on for some reasons why your DEF gauge reads empty when the tank is full: 1) Overfilling the DEF Tank. The first thing to know about filling the DEF tank is that it shouldn't be filled beyond the top of the tank.Def low warning light comes on one needle width below 1/4 tank. Less than 100 Miles later, at just above 1/8 tank, the dreaded 200 mile screw you Def message appears. Why does this 200 mile screw you message come up before the Def is empty or the gauge even reading empty? Why is the gauge not at all accurate?And of course you have three sensors in the tank that can fail or send faulty readings. This also brings up a key point and one on which I got conflicting information: 1. If the amber check engine light with just an outline of the engine is on, once you resolve the issues a few starting cycles will reset the light. 2.2024 First DEF fill-up. I got this message on my way to work this morning, it popped up with 500 miles DEF range. This is the first time I got a DEF message on the 2024, but I remember my 2020 would first come with a 1000 mile message. Anyway I filled up with 5.89 gallons and can say with current mileage it looks like I would have got 5,000 ...• The light bar indicates the level of fluid in the DEF tank. • Low DEF levels will trigger a decrease in engine performance. DEF level is EMPTY and IGNORED Vehicle speed limited to 5 mph / engine derated Flashing DEF level is EMPTY Vehicle speed limited to 55 mph / engine derated DEF level is very low Solid DIESEL EXHAUST FLUID (DEF ...Aug 8, 2022 · When the DEF light is blinking, and the engine check light is on, that means you have completely ignored the past warnings and have to refill the tank. Otherwise, the engine will derate. In other words, the engine won’t work until the DEF tank is full. Even after refilling the DEF tank, it might take 10-20 minutes to restore the engine’s ... 2020 freightliner M2-106 with 3 lights on.1 Check engine light. 2 Amber engine light 3. Amber low Def light with blinking red light. My def tank if full but keeps indicating i have no def fluid. Drove … read more I had an issue but was the 250 mile warning once after towing heavy and I put a jug of DEF in it and the low def warning WOULDNT go away. Corrected itself after a few days of normal driving so never go to Limp mode. Besides that put it back to stock. Drive it. Fill up the DEF. Disconnect the batteries overnight. Maybe that would help.PDI Big Boss CAT 3406E/C15/C16 Low Mount Exhaust Manifold. $1,895.00 Unit price / Unavailable. Choose options Choose options View details. PDI Diesel. PDI Big Boss CAT C15 Acert Exhaust Manifold. $1,895.00 Unit price / Unavailable. Choose options Choose options View details. PDI Diesel.

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If the low DEF light is on that probably is turning on the check engine like. The computer probably is being told your low on DEF even with full DEF tank Brandt , Aug ...Mar 8, 2023 · The DEF range DIC message first displays at approximately 1 600 km (1,000 mi). This message appears again at approximately 500 km (300 mi) of remaining range before the exhaust fluid tank becomes empty. As the fluid level nears empty, these messages appear every time the vehicle is started. If the DEF low warnings are ignored and the DEF tank ... Def low warning light comes on one needle width below 1/4 tank. Less than 100 Miles later, at just above 1/8 tank, the dreaded 200 mile screw you Def message …DEF will not reset to full. DEF shown low in DIC. Added one 2.5 gallon jug of Blue DEF which to my knowledge is API ISO 22241. DIC still reads low and mileage dropping. I got up this morning and added another 2.5 jug. Still no reset and now it's showing 98 miles to empty. When it lit the amber outline check eng light and the “Low DEF!” message appeared again, I topped off the tank (4.5 gal.) and the Low DEF message on the LCD cleared. I attributed this to cold temps and the lines maybe freezing since the DEF I added was warm (70* or so) and it cleared quickly. When empty it gives an 'exhaust fluid empty' message, and warns of future speed limit. 500 miles after that, it will speed limit to 65mph. 75 miles after that, it will transition to 55 mph. 75 miles after that, it will limit to 5 mph. 2023 LZO CC std box 4x4. previous: 2021 LM2 CC std box 4x4 ; '18 2500 L5P CCSB 4x4; '11 LML, '10 LMM and …Jun 4, 2022 ... Welcome to the first episode of ZK MasterTech shot in 4K. In this video, I tackle a DEF tank level issue and fix a noisy cab fan.May 7, 2018 · Technician: Andy. If you have insite, then look under data monitor Locker for the Def quality percentage. It should be sitting near 32.5%If it is out of whack then that will prove that the quality sensor is defective assuming it is only DEF fluid in your tank, and you will have to replace the entire DEF tank module. Dec 1, 2021 · 2017 F350 6.7 low DEF warning still on after filling DEF tank. I keep getting a low DEF warning with XXX miles left every time I start my truck. I filled the DEF tank, but not absolutely to the top from the bulk DEF pump at a Road Ranger. My gauge shows full, but I keep getting the warning. To perform an adblue reset in a 2014 vw passat tdi, turn the ignition to on without starting the engine. Push down on the gas pedal and keep it down until you see the glow plug illuminate again. Wait for it to stop blinking and turn off the ignition. Wait 10 seconds, turn the ignition back to on and press the gas pedal down two times.To be honest, not very far. Once the DEF light comes on you may only be able to drive between 50 and 100 miles, depending on your vehicle and the size of the DEF tank. Any further and your vehicle should go into limp mode and that is never any fun. To learn more about this situation, just continue to read our article.Yesterday I filled the def tank with eight gallons of def. This morning the def light is flashing along with the check engine and stop light on this 2015 freightliner. The def gauge says full. Company road service thinks I am stupid and put diesel in the def tank but at least is sending out a TA service truck to come see what is wrong with me. ….

Hi there. I have a 2017 Amarok V6. A few days ago a yellow warning sign starter to appear on the dashboard. Even after the full refill of the ad blue tank, the message keep staying with the km counter getting lower by days.The urea mix used in AdBlue/DEF also does NOT "crystallize" in partial tanks as some dealers might infer - again, no problems come up that require tank top off before that low level light, really. The reserve level in that AdBlue/DEF tank once you hit that light is around 2000-2500 miles.DEF Light on But The Tank is Full Peterbilt. On location when you see the warning light, even if the tank is full, is that there is a problem in the after-treatment system. That was the good news. The bad news is that there are about 250 items that can turn the warning light on even though the DEF tank is full.Oct 17, 2021 ... Freightliner Cascadia Blinking Def Light w/ Codes and Derate. Geared Low ... X15 DEF Tank Level Quality Temperature Sensor Preventative ...2. BMW did issue a 'bulletin' which says they will only do DEF with an CBS -based oil service- HOWEVER, the terms of the contract (ie the maintenance plan in you manual) says they will only do services when advised to do so by the car's CBS. A low DEF warning on the dash IS, in fact, a Conditon Bases Service indicator.Get a working scan tool that can reset a DEF system and plug it into the scan port beneath the dashboard on the driver’s side. Turn on the scanner and navigate to “Module Setup.”. Then, go to “Reductant Fluid.”. Thereafter, move to “Tank Level Reset” and reset the system. This will reset the warning to “None.”.Any of these mistakes could cause the DEF gauge to read empty. You should always leave a third of the DEF tank empty. Read on for some reasons why your DEF gauge reads empty when the tank is full: 1) Overfilling the DEF Tank. The first thing to know about filling the DEF tank is that it shouldn't be filled beyond the top of the tank.Installing low-voltage landscape lighting in your yard isn’t hard and makes a good DIY project. Expert Advice On Improving Your Home Videos Latest View All Guides Latest View All R...The problem is you are filling it too soon. Let it run down more and then it will reset better. As it stands now it may go away after a day or so. In the information screen it should show full or 1/2. That is about it. Normally it does show full or 1/2. As it stands I'll be limited to 80 kms/hr in 45kms. Low def light on but tank is full, Yellow warning light – this AdBlue warning light illuminates before your tank is empty to give you time to fill it up. It goes off the moment you refill the tank with exhaust fluid. Red light – this is the no restarting sign and illuminates when you fail to refill your tank with exhaust fluid. When this light is on, you won’t be able to ..., Mar 4, 2021 · Ok I’m at the mechanic now his telling me I should replace my whole system but I don’t think that’s the issue It’s saying code 3712 but my truck is saying low level of def. On your issue. If the def level is reading low and the tank is full I would check the wiring by the pdm. If there is no issues present then I would replace the QLS ... , I’m on the road and the check engine light came on.So I stopped found the low def warning on but 3 green bars on the dash So I added some, got four bars, the …, The first thing you should do is check your DEF levels. Low levels of DEF can cause the warning light to come on. To check the levels, locate the DEF gauge in your vehicle’s dashboard and ensure that it is above the minimum level. If it is below the minimum level, refill your DEF tank with certified DEF. Locating Certified DEF, The low Def yellow light is flashing even though it is topped off with def, 2013 dd15. 515hp, Yes, The check engine - Answered by a verified Technician ... Best advise I can give is to at least dump the tank and refill. Do a park regeneration every day. ... Low def light flashing but full of def, ..., Springfield, VA. TDI. ‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e. Nov 24, 2014. #4. The DEF tank uses a three-position level sensor (four electronic probes). Add a few liters of fluid, then turn the ignition on for 30 seconds. The system will reset the low fluid alarm if enough fluid has been added to satisfy the sensor., When empty it gives an 'exhaust fluid empty' message, and warns of future speed limit. 500 miles after that, it will speed limit to 65mph. 75 miles after that, it will transition to 55 mph. 75 miles after that, it will limit to 5 mph. 2023 LZO CC std box 4x4. previous: 2021 LM2 CC std box 4x4 ; '18 2500 L5P CCSB 4x4; '11 LML, '10 LMM and …, 2. Sort by: Add a Comment. mapleleafr67. • 1 yr. ago. A couple of things to try. Assuming it's a VW ? I finally cleared the warning by placing the adblue status on the dash display …, Most diesel vehicles have a DEF warning light that turns amber when DEF levels are low and red when the tank is dry. One gallon of DEF generally lasts 300 to 500 miles, and most vehicles require one gallon of DEF for every 50 gallons of diesel fuel. Without DEF fluid, the exhaust system becomes clogged, and the powertrain control …, To check your DEF fluid level, thumb the steering wheel-mounted selector to exit whatever display program you're in and enter the "Vehicle Info" menu. See All 8 Photos. Generally on our 2020 ..., This can cause the DEF to be consumed at an inaccurate rate and/or the level to appear low, even if the DEF tank is full. DEF filter: If the DEF filter is plugged up or dirty it can cause inaccurate readings due to higher or incorrect pressures and flow rates. The DEF filter is located on the bottom of the DEF pump and is inside of a filter cap., The alcohol content of Bud Light is 4.2 percent by volume. The alcohol content of the original Bud Light is quite low compared to some other Bud Light varieties. The alcohol conten..., SYSTEM" warning light on if DEF is over half full. This is my work truck, its an Isuzu NQR chassis, engine is a 4HKI-TC. A while ago the EXH. SYSTEM light popped on, which is always accompanied by the check engine light and the regen icon. I'm not a diesel guy at all, but I researched the light and all I can find is just: 'an issue with the SCR ..., My DEF gauge would get stuck at 1/2 a tank for a few thousand miles and then I would get a low DEF warning and fill up. Dealer replaced the DEF tank. Currently at 1/2 tank DEF on the gauge with a box of DEF in waiting in the bed of the truck trying to see if I can burn the gauge down from 1/2 to 1/8th. Not sure yet if the issue is fixed yet or not., I’m working on a 2016 Peterbuilt 579. The driver went to go on a night run and the truck is full derate, Def light flashing. Codes say def Quality and fuel filter restriction. The Def quality harness has not been connected and is capped. I’m assuming because it’s a different Def pump but I maybe wrong., new def fluid. def gauge shows full. yellow empty warning light flashing. red stop engine light on. yellow engine light on. clean def harness connections. Technician: mobile-tech. Run the Def leak test with insite. It should build 130 psi within a few seconds., The DEF tank is full, or at least it's acting full. Yet the light is still on and I'm down to "250 miles until no start". The closest VW dealership to me is at least 300 miles away, I'm planning on going there in a couple of weeks but I'm scared the car is going to leave me stranded!, When empty it gives an 'exhaust fluid empty' message, and warns of future speed limit. 500 miles after that, it will speed limit to 65mph. 75 miles after that, it will transition to 55 mph. 75 miles after that, it will limit to 5 mph. 2023 LZO CC std box 4x4. previous: 2021 LM2 CC std box 4x4 ; '18 2500 L5P CCSB 4x4; '11 LML, '10 LMM and …, The Polestar 4 comes with a bold design choice to completely remove the rear-view window. Drivers will rely on a camera alone for reversing. Polestar introduced the Polestar 4, the..., I’m on the road and the check engine light came on.So I stopped found the low def warning on but 3 green bars on the dash So I added some, got four bars, the …, The battery warning light in your vehicle turns on when you turn the ignition key to the "on" position. As soon as you start the engine, the light goes off and remains off until yo..., The def gauge, also known as the diesel exhaust fluid gauge, is one of the sensors that indicate the amount of diesel exhaust fluid in the tank. It is a crucial component of the exhaust system that reduces harmful emissions. If the def gauge shows empty when the tank is full, it could signify a problem that needs to be addressed!, When that did not work, Ford was contacted and the dealer did several checks on the system, including wiring. They ended up changing out the entire tank and the level sense was supposedly correct after this, but here I am three weeks after this "fix," about 1200 miles, and the DEF level still shows full. Coincidentally, or not, the real …, Def light on, tank full. Thread starter kathie659; Start date Nov 13, 2023; K. kathie659 Veteran Member. Joined Oct 24, 2014 Location Pennsylvania TDI Jetta 2001 Nov 13, 2023 #1, Diesel exhaust fluid (DEF) is a non-hazardous solution used within a selective catalytic reduction (SCR) system to break down harmful pollutants (NOx) generated by a diesel engine. DEF is 32.5% urea, or aqueous ammonia solution, and 67.5% deionized water. The fluid is sprayed and then spread into the exhaust gas via a mixer before entering the ..., Apr 4, 2019 ... In this video I preform a DEF Level reset on this 2011 GMC. This is a fairly common issue on these trucks and a pretty easy fix. -Enjoy!, This answer varies depending on the fuel tank’s capacity since it is different from one vehicle model to another. However, in general, when the fuel gets less than a quarter of the fuel tank capacity, the light comes on. For instance, if your tank capacity is 45, then when the fuel remaining is around 11 liters, the fuel light comes on., Jun 26, 2011. #1. Problem with Sprinter van...DEF light is on even though the resevoir is full. What could possibly be the problem?? Thank you! sailquik. Well-known member. …, When the DEF light is blinking, and the engine check light is on, that means you have completely ignored the past warnings and have to refill the tank. Otherwise, the engine will derate. In other words, the engine won’t work until the DEF tank is full. Even after refilling the DEF tank, it might take 10-20 minutes to restore the engine’s ..., Feb 5, 2020 · Then got the message stating I had less than 300 miles left on def. Gauge shows 1/2 full. Refilled again at a dealership. They found no codes with scanners DIC message was gone. Not sure if they cleared the DIC or not. But after 3 restarts and only about 15 miles, I have the DIC message again, for 890 mile range for def. DEF tank is full. , The alternative to a new cluster is to mark up the dial with a sharpie pen to what the actual fuel level is, and put some black tape over the low fuel light. Then you’d know the actual fuel level at a glance, but would have to suffer the burden of not having a low fuel warning light. 2007 Nissan Murano and I am between 1/2 and 3/4 of tank ..., Low Def Warning, Check Engine Light and Malfunction Indicator Light (MIL) The above messages, icons came on after starting the coach yesterday. Tank was topped off last month with fresh DEF. OptiView Digital Instrument Panel currently reads 86% which seems low since I topped it so not sure if that means anything?, Prevent Crystal Formation: When a small amount of diesel exhaust fluid gets exposed to air, say if your tank is nearly empty, it can crystallize. Over time, these crystals can cause blockages. By keeping your tank reasonably full, you help prevent this issue. Cold Climates and DEF: The fluid will freeze at about 12°F (-11°C).