Please consider!
The DEF Sensor Simulator is not an off-the-shelf device. It was originally created by a team of automotive engineers as a proof-of-concept solution for bypassing malfunctioning DEF sensors. The project consists of a parts list and open-source control code, and anyone using it must assemble and program the simulator on their own.
These engineers chose one of our products as the hardware platform for their design: the Arduino-Based ECU Development Board with Dual CAN Bus Interface from Copperhill Technologies. This board serves as the only point of connection between Copperhill Technologies and the DEF Sensor Simulator project.
What the DEF Sensor Does
A DEF (Diesel Exhaust Fluid) sensor is part of the SCR emissions control system, which is found only on modern diesel-powered vehicles and equipment. The sensor typically measures:
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DEF fluid level
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DEF temperature
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DEF concentration (quality)
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Sometimes tank pressure
These readings ensure that the SCR system injects the correct amount of DEF to convert harmful nitrogen oxides (NOx) into harmless nitrogen and water vapor.
Why It’s Only for Diesel
Gasoline engines do not use DEF because they do not use SCR systems. SCR is required on diesel engines to meet strict EPA emissions standards starting around 2010 for on-highway trucks and later for off-road equipment.
Where DEF Sensors Are Found
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Heavy-duty trucks (Freightliner, Peterbilt, Kenworth, Volvo, etc.)
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Medium-duty diesel pickups (Ford PowerStroke, Ram Cummins, GM Duramax)
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Agricultural equipment (John Deere, Case IH, etc.)
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Construction equipment (Caterpillar, Bobcat, Komatsu)
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Diesel generators
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Diesel vans and delivery trucks
DEF Sensor Background Information
Modern diesel engines rely on DEF (Diesel Exhaust Fluid) systems to reduce harmful Nitrous Oxide (NOx) emissions and meet environmental standards. These systems integrate software, hardware, and DEF fluid to perform this critical emissions-control task. Recently, however, a wave of failures has hit one key component: the DEF sensor. The root cause of this widespread issue—sometimes referred to as the “DEF pandemic”—remains uncertain. Heat stress, design flaws, and semiconductor failures are all possible contributors.
Regardless of the cause, the impact on drivers is immediate and serious. A failing DEF sensor triggers an automatic and escalating engine slowdown known as derate, even though the emissions system itself continues to function normally. This derate can leave vehicles stranded on the roadside or force them to operate dangerously below the speed of traffic. Replacement sensors are often unavailable due to supply-chain shortages—especially the post-2020 semiconductor crisis, which analysts predict will affect availability well into 2022. As a result, trucks and equipment may sit idle for days or weeks. The irony is that the emissions system is still working correctly; it’s the sensor that stops reporting accurate data, causing the ECM (Electronic Control Module) to assume a system failure and initiate derate. Typical symptoms include a Check Engine light, accompanying fault codes, and eventual derate. Click here for details on the fault codes. Being unnecessarily derated in a diesel-powered vehicle is dangerous to its occupants.
DEF Head Alternatives Are Coming
Federally mandated DEF (Diesel Exhaust Fluid) monitoring systems have increasingly left RV owners stranded. The issue is multifaceted—ranging from widespread DEF sensor failures to ongoing microchip shortages, all compounded by slow responses from both industry and government agencies. As a result, we’ve received countless messages from frustrated RVers who either cannot use their vehicles or are afraid to risk a breakdown.
Fortunately, persistent and resourceful members of the RV community have not given up. Thanks to their efforts, two promising alternatives to the traditional DEF head are now emerging on the horizon, offering hope to those affected by this long-running problem. Read more…
DEF Sensor Workaround
If you’ve been following the saga of stranded RVers, the story has unfolded with the drama of a Shakespearean tragedy. Yet unlike the fates of Cleopatra or Macbeth, this tale may finally have a hopeful ending. Within just two months, a determined group of resourceful, never-say-die RVers has engineered a practical workaround that may put their rigs back on the road. By all indications, it’s a highly promising solution to the ongoing DEF sensor problem. Read more…
About the DEF Sensor Simulator
The DEF System Simulator (DSS) is a user-assembled hardware and software solution designed to provide a temporary workaround when a DEF sensor fails. Built from inexpensive and widely available components, the DSS allows drivers experiencing a derate to restore full engine power long enough to reach a repair facility safely. Once installed—and following the documented procedures—the DSS overrides the derate condition, enabling the vehicle to operate normally until a proper repair can be completed. Read more…
DEF Sensor Simulator – Quick Build
Since the original DSS solution was released in September 2021, the team has continued evaluating alternative hardware and software configurations. This page provides a brief overview of each variant developed so far, along with links to their respective build instructions. Based on factors such as cost, size, parts availability, and ease of programming, the team currently recommends the option listed in the Recommended section as the most practical choice. However, all build variants remain valid solutions and offer flexibility—especially valuable during supply chain shortages. Read more…
DEF Sensor Emulator Firmware and Assembly Manual
This repository provides the compiled Arduino sketches used to emulate a Diesel Exhaust Fluid (DEF) head, along with step-by-step instructions for assembling the emulator. The code is available precompiled for the Arduino DUE, Arduino UNO, and the ATmega2560 platform. Read more…
ANCEL Heavy Duty Truck Scanner HD601 All System Diesel Diagnostic Scan Tool
The upgraded ANCEL HD601 Heavy Duty Truck Scanner offers wider and more accurate compatibility, supporting all major diesel trucks using SAE J1939, J1708, ISO 14230-4, ISO 15764-4, ISO 9141-2, ISO 27145-4, and Euro 6 protocols. It works with engines from Cummins, Caterpillar, Detroit, Paccar, Perkins, MaxxForce, Allison, Eaton, Bendix and more, covering Class 4–Class 8 trucks from brands like Freightliner, Peterbilt, International, and Ford Heavy Truck. It can also perform engine diagnostics on most cars, minivans, and light trucks. The HD601 provides full-system diagnostics—including Engine, ABS, Transmission, Braking, Fuel System, ESP, and EPS—retrieving live data, freeze frames, vehicle info, and DTCs with included 6-pin, 9-pin, and 16-pin cables for broad compatibility.
Designed for both professionals and beginners, the HD601 features a built-in DTC library, a fast processor, lifetime free updates, and an easy-to-read 2.8″ color LCD with improved navigation buttons. The plug-and-play design makes it simple to locate faults and understand code definitions, helping users save time and money on repairs. Plus, each purchase includes lifetime technical support, a one-year warranty, and a FREE official storage box (valued at $24.99) when added through the “Bundles with this item” option. More information…
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