How to a Reset Mercedes Sprinter DEF Light

The diesel exhaust fluid (DEF) is an emission control fluid that’s automatically sprayed by the van into its exhaust system to neutralize nitrogen oxides present in exhaust fumes to nitrogen and steam. It’s present in Mercedes Sprinter diesel engines to meet EPA emission standards.

Once the fluid is low, you’ll get a notification to refill the DEF/ AdBlue tank. The warning light ceases once you’ve refilled it. However, sometimes the warning light persists and may need to be reset.

Here is how you can reset the Mercedes Sprinter DEF light.

  • Turn ignition to the first click
  • Depress gas pedal until glow plug comes on
  • Release it and see if the glow plug light flashes
  • Turn off ignition once it stops blinking and wait for 10 seconds
  • Turn ignition back on
  • Press the gas pedal twice and depress it on the second attempt until the glow plug is on

That should reset your Sprinter van DEF light.

It’s important to note that you can only reset your AdBlue/ DEF light once you’ve refilled your van. It isn’t possible to reset it when the van senses the DEF is below the minimum allowable level.


Mercedes Sprinter Consumes 2.4 – 4.0 Liters of AdBlue Per 1,000 km/ 620 miles

All diesel-powered Mercedes Sprinter vans use the AdBlue Diesel Exhaust Fluid (DEF) to lower their carbon footprint and nitrogen oxide emissions. The vans very  efficiently spray the DEF into their exhausts.

Therefore, depending on your driving style, the road conditions, the state of your van’s drivetrain, and traffic, your van consumes 2.5 to 4.0 liters of AdBlue per 1,000 kilometers.

And, as they have a 22-liter AdBlue tank, expect to refill your AdBlue tank every 5,500 to 8,800 kilometers. Mercedes recommends draining the tank and refilling once every 32,000 kilometers or 20,000 miles.

Keeping that in mind can sometimes be challenging, as road and loading conditions vary. Luckily, you’ll get a “Refill AdBlue” message and a fixed number of starts or distance before your car stalls on your instrument panel when the van is running low.

Operating a van that’s too low on AdBlue is illegal since it won’t be meeting the EPA emission standards. And, to safeguard themselves from the massive lawsuits that shall follow, Mercedes programmed all its diesel vehicle engines, Sprinter van included, to cease running until you refill the DEF tank.

You don’t need to panic if you get a Refill AdBlue warning, as it’s a message that states what you should do. It’s not a sign of an underlying problem within your van’s engine, transmission, or exhaust system.

Your van will resume normal operation once you’ve refilled the AdBlue tank. And, to be on the safe side, refill the tank every time you get the first warning. If the AdBlue runs out, you’ll get a “Refill AdBlue Start not possible” message on your instrument panel.

To resolve the warning, you need to top up the fluid with a minimum of 3 liters of Mercedes-grade AdBlue.

And as Sprinter DEF tanks are 22-liters/ 5.8 gallons, you will spend anywhere between $31 to $40 to refill the tank.


How to Refill Your DEF Tank

Even though DEF is a harmless and non-toxic fluid, you need to be very careful when handling it. In case of a spill or contact with the fluid, wash the area with clean water, and avoid opening your DEF cap if the engine is still hot.

Some ammonia vapors may escape through the opening. Prolonged exposure to ammonia causes burning of the eyes, nose, throat, and respiratory tracts.

Now that we have gone through the important safety measures, here’s how you can safely refill your DEF tank

  1. Remove the key from the ignition and pull the hood release latch that’s to the left of your brake pedal.
  2. Open your van’s hood and locate the blue AdBlue/ “DEF only” lid and open it
  3. Fill the DEF tank using a filler neck until you can see the DEF fluid level through the filler neck
  4. Once you’re satisfied, replace the filler cap and turn it clockwise till it’s tight
  5. Most importantly, make sure that no impurities get into the AdBlue tank. Impurities such as water and diesel will interfere with its normal functioning, causing engine and exhaust problems.


Where to Buy DEF / AdBlue for Your Sprinter Van

Some places where you can buy AdBlue for your van include:

  • Retail stores
  • Dealerships
  • Service stations

The two good places to buy it are dealerships and service stations. The containers are easy to use and fit exactly with your Sprinter van’s AdBlue tank filler cap.

And always remember to refill your AdBlue in an open, ventilated area to avoid ammonia poisoning.


The Sprinter Van DEF System Is Complex and Expensive

The Mercedes Sprinter DEF system is one of the most complex and painfully expensive systems in your van. So, if your Sprinter tells you it needs an AdBlue top-up, listen to it.

Sprinter vans use the exhaust gas recirculation (EGR) strategy to control nitrogen oxide (NOx) emissions.

The EGR unit has a valve that controls the flow of exhaust gasses being recirculated from the exhaust manifold and into the engine’s intake manifold. Therefore, fumes from the exhaust must pass through the EGR valve before getting back to the engine in small amounts.

In this way, your van reduces the NOx it’s emitting to the environment.

The third and final part of the DEF system is the exhaust system. It comprises two SCR Cat parts, the Oxi-Cat, and the DPF. The OXI-Cat has two sensors; the exhaust gas back-pressure and  sensor.

You’ll find an additional nitrogen oxide sensor and a dosing valve between the OXI-Cat and the SCR sections. Once the exhaust gasses get past the DEF system, it’s passed on to the diesel particulate filter (DPF).

The role of the DPF is to trap soot from your exhaust gasses. Most Sprinter vans that emit black smoke have faulty DPF filters.


Here’s How DEF/ AdBlue Works in Your Sprinter Van

The van stores the AdBlue in a DEF tank and injects it into the exhaust pipe through nozzles between the engine and the selective catalytic reduction (SCR) system. When hot gasses pass through the exhaust, they encounter the AdBlue vapor, heating it into ammonia.

Ammonia is highly reactive and will decompose the nitrogen oxides present in the exhaust gasses to form nitrogen and steam.

Nitrogen is a harmless gas and is the key component of the air we breathe in.


DEF Neutralizes Nitrogen Oxides in Exhaust Gasses

Sprinter vans have the Mercedes-Benz BlueTEC badge showing that they meet set environmental standards without compromising their performance.

AdBlue is a highly pure, non-flammable, and non-toxic urea solution comprising 32.5 percent synthetic urea and 67.5 percent demineralized water.

You can only use it in BlueTEC vehicles, only the diesel vans have them, all gas-powered Sprinter trims lack an AdBlue tank.


3 Important Tips When Dealing With The DEF

DEF is a highly pure substance that should be free of contamination at all times, whether it be in your Sprinter’s DEF system or storage.


Don’t Put DEF in a Fuel Tank

A common and costly mistake is filling your main tank where the fuel goes with DEF liquid while at the gas station. DEF corrodes parts of the fuel system and when contaminated, you’ll have to replace the fuel pumps, injectors, and filters.

Once you’ve acknowledged your mistake or you’re in doubt, don’t start your van. Tow it, drain the fuel tank, flush it with diesel, and add new fuel before starting it.

Running on a DEF and diesel mixture is very costly and damages the engine once it reaches it.


Avoid Contaminating the DEF

Purity is crucial for the DEF to work well. When adding it to the DEF tank, inspect the area around the cap, and wipe it clean if necessary. Also, watch out for dust floating in the air or water.

Any contaminant will cause the selective catalytic (SCR) system to malfunction, and your van will go into limp mode. And as your van detects the AdBlue is impure, it will have to shut down once the grace/ limited-start period is over.

From then, you’ll need to tow your van to a Mercedes dealership or repair shop to flush out the impure DEF.

Impure DEF will affect the performance of the SCR in the following ways:

  • Loss of effectiveness in removing the nitrogen oxides from exhaust fumes
  • Increased DEF consumption to compensate for its inefficiency
  • A malfunctioning SCR and exhaust system
  • Engine shutdown
  • You may void your manufacturer’s warranty


Store Your DEF in a Cool Dry Place

Store your DEF out of direct sunlight and preferably indoors. The DEF degrades gradually, but can last more than a year if stored between 12 and 86 degrees Fahrenheit.

And since it’s a delicate fluid, I don’t recommend buying it in bulky storage containers; buy it preferably in 2.5-gallon containers.



Mercedes BlueTEC technology combines three highly sophisticated technologies that work in tandem to ensure that your Sprinter van meets the emission standards. It includes a variable-vane turbocharger, high-pressure fuel injection, and AdBlue/ DEF technology.

The DEF in a Sprinter is vital and ensures that your van doesn’t sacrifice its raw power for cleaner emissions.