How to Bypass a DEF Level Sensor?

If you too get distressed by frequent DEF maintenance and want to find a way around it, or are you hearing this word for the first time? Do not worry, we are here to help you with everything that you need to know about this particular setup involved with almost all diesel engines.

If you own a truck, RV, or any other vehicle that has a diesel engine, it would most likely be equipped with a DEF sensor.

What’s a DEF sensor? How does it work? And how you can bypass a DEF level sensor? Let’s answer all your queries in detail.

What is DEF Sensor and How Does It Work?

DEF stands for Diesel Exhaust Fluid. It is an assembly containing a mixture of liquids in the exhaust system of all new diesel vehicles.

To reduce carbon footprint and pollution created by diesel engines, all new vehicles are required to be installed with a DEF sensor. It is an amalgamation of 3 different sensors that tell the level, quality, and deration of DEF in the exhaust.

It contains a combo of urea and ionized water that combines with exhaust gases and reduces the toxic particulate that gets emitted into the environment.

Why Do I Have to Bypass DEF Sensor?

As these fluids are volatile and highly reactive, they can corrode the metal in your car’s exhaust and there are other issues associated with it as well.

For instance, if DEF is running low, you can’t drive above the 5 MPH speed limit and it also costs good money to keep the tanks filled up. The DEF system is also known to give frequent problems like system failure, error codes, and reduced engine lifespan.

Legally, you can’t drive on roads with the DEF system bypass or disengaged, so please do it at your own risk.

5 Easy Ways to Bypass a DEF Level Sensor

Here’s how you can easily bypass a DEF level sensor:


Software Update

This is by far the easiest and most reliable way of getting around your DEF level sensor. As it is in conjugation with your vehicle’s ECU and regularly sends data to it, you could get rid of it via a software update available on the market.

This is a recent intervention introduced by the aftermarket developers and can help you bypass the DEF level sensor without any mechanical intervention. You don’t have to remove any part or component of the exhaust system and it also keeps your warranty intact.

Look for the latest software updates available and the best source of that is the trucker’s or off-roaders’ communities online.


Speed Sensor Removal

The main problem faced by most RV owners is that they can’t drive on low DEF, and soon as the low-level indicator kicks in, they can’t drive above 5 MPH.

Once getting off the road, there’s so much going on and you’re already neck deep in luggage and equipment, you can’t carry DEF or find it around out there.

The best idea in that situation is to remove the speed sensor from under your RV and use a GPS to follow the speed limit. This way, you’d be able to drive your vehicle without any errors, warnings, or limits.

Although it’s an easy fix, use it only as a temporary way out and not a permanent solution. You could land in serious trouble for meddling with your vehicle’s safety and ignoring the DEF sensor.


Windex Treatment

Windex is another way of bypassing the DEF level sensor on your diesel-powered motorhome, truck, or SUV.

The ideal way is to drive down to a nearby mechanic, get your exhaust disassembled and get the DEF assembly treated with Windex. This is a relatively newer method that’s been introduced in the market and can help you get rid of issues associated with DEF.

There is no long-term feedback or research available on the efficacy or cons of Windex Treatment. So you should consult your local mechanic before putting your RV through it.


Replacement of Exhaust Assembly

Needless to say, if you change the whole exhaust assembly in your vehicle, you won’t have to worry about DEF as it would not be there.

This is definitely the easiest and most reliable way of bypassing a DEF-level sensor. But keep in mind that it could be expensive as exhaust systems are not cheap, especially the ones that offer DEF bypassing.
It is also prohibited by law (DMV) to remove your DEF system or replace the exhaust system, so be careful about making this modification. It could also could your manufacturer’s warranty and make things worse in the future.


DEF Delete

If you’re looking to bypass the DEF level sensor on your vehicle, DEF delete might be the last resort for you. Just like EGR delete and other exhaust bypass systems, DEF delete is an easier way of bypassing it.

It could either be done via a software update or mechanically using a delete kit. Both of these solutions are aftermarket and not offered by any official manufacturer. The software update is the easiest way of bypassing your DEF level sensor and could prevent you from any legal trouble on road, in comparison to using a kit or getting rid of the system itself.


DEF, aka diesel exhaust fluid, is similar to AdBlue used in some European countries and is aimed at reducing carbon emissions. The target of this intervention was the heavy-duty commercial diesel vehicles but have slowly become necessary for passenger vehicles as well. If you’re looking to bypass the DEF level sensor, use any of the above-mentioned methods that we just discussed. No matter which trick you use, remember that it is illegal to drive your vehicle without a DEF sensor and you could land in legal trouble for interfering with this device.

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