DEF Sensor Simulator – Quick Build

While there are many variations of hardware and software for this project, this page focuses on one method that is proven to work on the majority of tested motorhomes and endeavors to keep the construction process as straightforward as possible.

Only basic electrical and DIY skills are required for the hardware assembly, no soldering is needed. The software installation in this procedure requires a Windows system and only involves typing some simple commands.

Before you begin, please click here to read an important compatibility notice regarding the ECM (Electronic Control Module, aka Engine Computer) and info on compatible DEF head connectors.

If you run into difficulty see the Troubleshooting section for more info or contact the developer. You may also post comments to this page if you have basic questions. Non Windows users may also want to keep an eye on the Info & Options section for alternatives.

Parts – order these items:

  1. Arduino Due with Can bus & Extended Power – from Copperhill Technologies
    Note: Be sure to click YES for the Extended Input Power Range Option! The cost should be $96.95 delivered with the Extended Input Power Range option. If this board is out of stock you can order the alternative found here. The alternate has sold out as well. So you  will need to order 2 pieces, the first is the Arduino by itself and the second is the CAN Bus daughter board from Copperhill. Both of these items are found at the following links:

    1. Arduino Due Board – Add the option of  USB Cable Type A Male to Micro Type B Male

    2. Dual CAN Bus Interface For Arduino Due With Extended Power Range

      Arduino-Based ECU Development Board With Dual CAN Bus Interface

  2. DT-4 Extension Cable – from Diode Dynamics $15 + shipping
    DT 4-Pin Extension Wire
    Note this connector style will not be correct for all applications:
    – Freightliner owners please see this page.
  3. Waterproof Enclosure – from Amazon $14.99
  4. Optional PG-9 size Waterproof Cable Gland – from Amazon $0.70 This item can also be found at most local hardware stores, auto parts stores as well as some Home Depot and Lowes.


  • Drill
  • Wire cutters / Strippers
  • Small screw driver
  • Ohm meter
  • Silicone (or Weather Gland)
  • 5/16″ drill bit (if not using weather gland)
  • 9/16″ drill or step bit (if using weather gland)

Download the software:

Download the following file to your windows desktop – DEF Sensor Simulator Install Files 

Make sure you remember where your download went to (Downloads, or Desktop) you will need to know where it is at later.

If you get a message indicating the download will harm your computer (it won’t that is just because it is new and not officially recognized by windows), see here and/or this 16 second video for instructions.

Extract and install the software:

  1. Plug the USB Cable into the Programming Port of your Arduino Board, port closest to the power connector. The cable will provide power to the board and facilitate the data transfer.
  2. Plug into a USB port on your computer.
  3. Open the device manager on your PC, expand the Ports (Com & LPT) group, make note of what usb com port your Arduino is on. You can Unplug and re-plug the connector on the Arduino or your PC to verify which port it is using. Write this port number down. LEAVE the Arduino PLUGGED into your USB port.
  4. Extract and install the software that you downloaded by double clicking the package that you downloaded called DEF Emulator Install Files (x32).exe. Note: When opening the file, you might get a “Windows protected your PC” message box -> Click “Run anyway”. If prompted “Do you want this file to make changes to your hard drive?”, click “Yes”. See here for more info.
  5. Answer Next to all the extract to directories, do not change the install directories they are needed later.
  6. Right mouse click on the start button on the task bar, choose Run.
  7. In the Run command box Type CMD and press enter or Select OK
  8. In the open command prompt windows dialogue box type the following: c:\AVRprog\program.bat DUE 6     
    Note: you will need to change the number 6 in the above example to the com port number you wrote down in step three now press Enter.
  9. You should see something similar to the following:
  10. And when it is finished:
  11. When the install has finished, unplug the Arduino from the USB cable, the computer stuff is done.

Assemble the hardware:

  1. Take the 1 Meter DT Extension cable that you purchased in Hardware step 2 and cut the off the flat end with the exposed orange silicone as shown in the picture below, approximately 6 inches from the connector. The short end with the Orange silicone connector will not be used electrically, but if desired can be used as a “dust cap” for the DEF head sensor connector when the DSS is in use.

    Note: Freightliner applications will require a different connector/cable – for more information click here.

  2. Take your waterproof case and drill a hole 3/8 in size in the upper corner (large enough to pass the cable through. Alternately drill a hole large enough to accept the weather gland (9/16) and install it now (weather gland shown in photo).
  3. Trim the main wire covering about 2 inches back, careful not to nick any of the individual wires.
  4. Trim and strip ¼ of insulation off each wire and go ahead and twist the bare wire to keep it from fraying out.
  5. Just in case, it is suggested to identify the correct color coding using an OHM meter. Put your meter on the ohms scale and test each pin to ensure continuity to the appropriate colored wire. Looking at the business end of the plug:
    1. Top Left +12 (Should be Yellow)
    2. Bottom Left Ground (should be Blue)
    3. Top right – Can L (should be Red)
    4. Bottom Right – Can H (should be Black)
  6. If your colors are different that is ok just make note what function each color is for (+12, GND, CAN-H, CAN-L) – the position on the connector is what is important.
  7. The Arduino DUE daughter board (opposite end from the usb connection ) has green screw terminals and is marked with the following: VIN, GND, 2H, 2L, GND, 1H, 1L, GND. You will only be using VIN, GND, 1H, 1L. To prepare the green terminal blocks for inserting the wires, it is best to make sure they are fully open as shown below.
  8. Using the photo below, or the wires you identified in step 5 if the color coding is different wire it up as shown below. Note: It may not be obvious, but the green part with the screws unplugs from the green part on the circuit board so go ahead and remove those connectors, it will be much easier to attach the wires.
  9. In the step above use plenty of light and a magnifier if necessary to make certain there are no errant strands hanging out of the screw terminals that could potentially cause a short. It is OK to cut off a few strands if needed to make the wires fit easier, especially on the thicker wires.
  10. Disable the termination resistors by removing the jumpers shown in the photo below.
  11. Adjust the length of main wire in the weatherproof box to position the Arduino in the box.
  12. As a final test use your OHM meter to double check you have continuity from the each plug pin to the appropriate Arduino connection.
  13. If you did not use a weather grommet on the cable then now is a good time to place a dab of silicone on the opening of the box where the wire passes through.
  14. Your Def Sensor Simulator build is complete.

Connecting to your motorhome CAN network:

  1. Make sure that before you unplug your def head that the ignition is turned off, then unplug your def head. You may need to cut a zip tie to provide working slack in the wiring.
  2. Plug the simulator into the connection to your chassis wiring where the def head was plugged in.
  3. Turn on your ignition, some or all of the fault codes should go away and the Check Engine and MIL (Malfunction Indicator Lamp) lights should extinguish within a few minutes.
  4. If some codes remain, to clear your codes you will need to turn your ignition on (let all systems come up, about 20 seconds), then start your engine and fast idle for 5-6 minutes, shut down for 90 seconds, turn ignition on (wait for systems to boot 20 sec) start engine and fast idle for 5 min. You will do this a total of 3 times on the 4 cycle the codes should clear to the inactive status.
    Note: on older engines or engines with older ECM software, some codes may not completely clear on their own. In this case code clearing intervention may be required. This is something that is still under study, see the Troubleshooting section for more info.

124 Comments to DEF Sensor Simulator – Quick Build

  1. […] To get started with building your own DSS as quickly as possible go to the Quick Build page. […]

    • Don Rackley says:

      Nicely done! Thank you.

      After I have read through this I have 3 minor questions, perhaps you can help.
      1. In the step where you plug the Arduino into the computer, you reference a USB cable, does this come with the Arduino or do we need to buy it separately?
      2. I do not see any reference about fastening the Arduino inside the weatherproof box. Did you do that of just leave it to jostle around? Should I wrap it in anti static bubble wrap or use nylon screws through the box and standoffs?
      3. I did not see a note about how the completed assembly was fixed to the coach. I assume cable ties around the plastic box are to be used?

      Thank you for the excellent solution to an uncomfortable problem.

      • Voltdoc says:

        Excellent questions thank you for bringing them up!

        1) Yes, the Arduino DUE purchased from Copperhill comes with the needed USB cable.
        2) Regarding fastening the circuit board to the housing box there are a few options, but open to ideas.
        a) The Arduino DUE circuit board comes with a plastic tray that covers the bottom of the board. This tray fits fairly tightly but could be attached to the board with small screws or double sided tape. Then that assembly could be attached to the bottom of the housing with velcro or double sided tape. Keeping in mind the board will need to be removed to get to the micro-USB connector for any future program updates.
        b) Plastic standoffs that stick to the bottom of the box and snap into a couple of the mounting holes in the Arduino board, at the moment we don’t have a recommendation for a specific product, not sure if anyone has tested this approach yet.
        3) Regarding attaching the completed assembly inside the DEF bay. This will be dependent on the specific coach. Ideas are magnets, velcro, zip ties and duct tape. In my own case I have a lot of steel nearby on my coach so I’m considering using a couple of neodymium magnets attached to the bottom of the box with 3M double sided tape. Self stick velcro will also work in most applications, or just zip tie the cable or box to something appropriate nearby.

        If you or anyone else have ideas please comment back!

      • Archer2 says:

        Don, all good questions. Voltdoc is correct that the Copperhill Arduino Due comes with a USB cable, but not all boards do. Check the description for your board to verify.

    • Ken Mahler says:

      I have a question about removing or repositioning the jumpers on the Arduino Board. In photo step 1, it shows removing one jumper. Does it need to be removed before programming? In step 10, it shows removing two jumpers. Just want a little clarification on when to removed jumpers. Thanks.

      • JWP says:

        Hi Ken, the jumper do not have to be removed before programing. These are termination jumpers that only have an impact when it is connected to the Chassis Can Bus network.

    • Tom Schleis says:

      My Arduino board came without a green plug for the VIN and GND. Has anyone else found this?

      • Voltdoc says:

        Hmm, that’s not good. If you haven’t already, suggest you contact the seller for resolution. Also could you share where you bought it from?

    • Steve lamothe says:

      So can anyone confirm that this is the correct board, I’m only questioning because I do not see anywhere to “click” the extended power option on Copperhill website.

      • Archer2 says:

        I can’t see what you are looking at but I believe Copperhill is back ordered (and very expensive). Take a look at the alternate hardware (UNO) build instructions here
        The main difference is that this requires assembling a DB9 connector. It’s not very hard if you splice 4 small-gauge wire extensions to the main connecting cable to make assembly of the very limited space DB9 connector more manageable.
        The UNO with the Seeed CANBUS v2 performs exactly like the more expensive Copperhill DUE+CANBUS interface. You should be able to buy the hardware from your choice of sources like Amazon, DigiKey etc.

  2. PETER G RIBBENS says:


  3. Duane Gordon says:

    Thanks to all who contributed to this solution. I was stranded in Tennessee for four days and a cost of $2000 plus dollars two years ago for this same problem.

  4. Jay Witthuhn says:

    Thanks to all that developed this! Question: Which chassis (Freightliner, Spartan, other?) has this been tested on?

    • Jwp says:

      Spartan chassis basically with the Shaw def head, 450 and 605 Cummins. We have also tested on an Int 4300 and Tiffin Powerglide.

  5. JOSEPH ZINKEL says:

    I have been following this issue and see a temp. fix has been put together.
    Thanks for all your work on this
    When trying get the parts to assemble this, I have run into a back order on the Arduino due from Copper Hills. They are not expected back in stock til end of October. We will be on the road and not able to receive. Due you know of any other sources?

    Also, Cable gland is also out of stock

  6. Wold says:

    Thank you for taking on this project and especially for providing the results of your efforts it in this mannner. The computer age left most of us hobby mechanics incapable of dealing with being stranded by faulty sensors. I’ve been there three times with no help form those responsible for this problem. You’ve gone above and beyond and done the right thing when others wouldn’t.

  7. David Telenko says:

    Greetings, thanks for putting the DEF fix together, seems easy enough to do, well if you have a PC. I myself have a Mac & I have several friends that only use smart phones!. So how are we supposed to do the necessary programing? My biggest concern is showing its ugly head already “PARTS”! Only makes sense that the parts are going to be hard to impossible to get. Thats why the auto manufactures & all others using chips or other electrical components are shutting down their plants! I’m hoping that maybe, just maybe that the necessary parts are made here in the USA & will be available!
    I’m not trying to be negative, just a realist to whats going on in our world.
    Thank you
    Dave Telenko

    • JWP says:

      Dave, We will be posting the instructions for a MAC very soon, as for the smart phone users, find a friend with a tablet or a laptop.

    • JWP says:

      Dave, Thanks for your concern. We have posted the alternative board and provided several other build options on the site. The parts are available sourced from US vendors. We will be posting the MAC instructions for programing shortly. As far as the smart phone users go, this would be a great time for them to make a friend with a person who has a laptop, tablet or Desktop computer with a USB port. This project is a DIY, not a one stop product purchase.

  8. Daniel G. says:

    Dave, I have a 2016 Dodge Ram 2500 6.7 Cummins Diesel, that pulls a 36 foot fifth wheel. Does all this information also apply to my truck. Thank you ahead of time.

    • JWP says:

      Daniel, The answer your your question is both yes and no. This project and the specific programing does not apply to your truck. The concept of DEF and the failures along with basic Def system design does apply to your truck. This Simulator will not work on your truck.

  9. Ed Puglise says:

    I’ve been running into DEF issues with my 2015 Duramax. After many visits to the dealership, one derate notice, and finally replacing a nox sensor, it seems like I’m back on the road. (With a lighter wallet).
    Couple questions:
    You’re mentioning Cummings engines but nothing about Duramax or other truck diesels. Do your fixes work for them?
    Any talk if manufacturers are going to extend their warranty?

    • Voltdoc says:

      Sorry this won’t work for your vehicle, the DEF simulator solves only a very specific set of faults generated by a failed DEF head sensor (most commonly made by Shaw). It does not address issues related to the NOx sensor. It has not been tested on the med duty engines and probably wont even hook up to them in this configuration. The connector and ECM programming may be OBD instead of J1939 and the DEF system is very likely to be different as well.

  10. Glen Allen says:

    Looks like a great solution Thanks for doing this. As you know the primary part is out of stock. You made a point of saying to select the extended power option on it. The alternative board you listed does not have an extended power option and I can’t find the input voltages in the specs. Is it OK to just order the alternative as listed? Thank You

    • JWP says:

      Yes the alternative part will work fine for this project.

      • John C. says:

        Another question came up for me while looking at the alternative board. That board does not have the same jumper pin location. Is there a particular setting on the alternative board. It looks like a more sophisticated board and a little more expensive. Also can the alternative board accommodate an LCD display. You example was off the first Board.

  11. Charles von Beck says:

    AsI tow with a 2019 RAM 2500 Diesel do they have the same issue? Might build one for emergencies.

    • JWP says:

      Charles, Although you have a Cummins Engine and the Doge Rams have also had DEF issues, this solution in its current form will not work for you. The coding for the ECM is different.

  12. John C. says:

    Another question came up for me while looking at the alternative board. That board does not have the same jumper pin location. Is there a particular setting on the alternative board. It looks like a more sophisticated board.

  13. Tom says:

    Wow. I appreciate you guys doing this. I ordered the parts before checking compatibility. I see the parts are flying off the shelves. Cable is back ordered, but I’m not in a rush. I am pretty sure my coach has the potential for sensor failure (Tiffin with ISB6.7 on Powerglide). It hasn’t happened yet, but I expect it will at some point, so I want to be prepared. I copied the content of your instructions to a Word file. Crazy world we are living in. Hoping the government doesn’t come in and shut your site down. Never ever would have expected it until 2020/2021 rolled around. Yes, I’m a bit paranoid these days. Thanks for your help!

    • JWP says:

      Thanks Tom, you can also order just the connecter with pig tail and use 16ga wire to build your own cable making sure to use waterproof connection as well.

  14. Val says:

    Hi, is it works with Cummins X15 engine ?

  15. William Whitenton says:

    Wondering if my coach is effected. It is a 2010 tiffin allegro bus on the powerglide chassis. The whole def contraption was replaced back in 2019.
    Also, i could not get the software to download. I got a message that the software could harm my computer.

    • JWP says:

      Yes your coach has the earlier version of def implementation on it. We have seen very few failure in comparison to the newer coaches due to the type of sensors used. On the software download, when the warning pops up depending on the OS version you should have the option to show details when click on the detail the option to keep or to download anyway will appear. Click keep or download.

  16. Michael Schwarz says:

    The alternative item #2 (Dual CAN Bus Interface For Arduino Due With Extended Power Range) is also out of stock. Are there any alternatives that will work?

    • JWP says:

      Michael, Yes there is, on the Right hand side of the page if you click Build It, scroll down to the bottom and you will see the build for the UNO and Mega.

      • Michael Schwarz says:

        Sorry to be a pest. I can’t find the term ‘build it’ anywhere on the Copperhill Technologies web page. Not sure what UNO and Mega means. I tried a search for them together and didn’t get any results. Can I get a few more details?

  17. Michael Schwarz says:

    The DT 4 pin wire is also out of stock at 1 meter, but the 3 meter version is available. Other than extra wire, is that a problem?

  18. Ken Colby says:

    Just wanted to say how grateful we are to all that have contributed to this issue as well as everyone that has submitted a complaint to NTHSA, EPA, Cummins,Spartan, Freightliner etc. I have ordered all the items suggested and just awaiting arrival now to start my build as there is no telling when Cummins will release some type of programming update.

  19. Stu says:

    I received the last of my parts this afternoon and in about half an hour I had the project completed. I’ve used Voltdoc’s instructions before for a different project and very much appreciate his concise, thorough instructions.

    Since my DEF head was working when I last shutdown the ISL 450 in my 2018 Spartan K2 chassis, I’ll hold the simulator as an insurance policy against possible future failure.

    I’m so grateful for the efforts of an enterprising group of individuals who put this insurance policy together!

  20. Kelly Fitzpatrick says:

    I see that all the options are backordered for the Arduino canbus adapter. I have a spare Raspberry Pi 3 and canbus adapter I used to interface to my 2019 Phaeton Spyder system, until I upgraded to a beefier RPi4 version. How complicated would it be to port to Raspberry Pi? Could you provide the low-level canbus timing settings and command sequences if I wanted to take this approach? Or is that info already available in your download package? Thanks!

    • Voltdoc says:

      Not right now, only the Arduino hardware specified is currently supported. There are no immediate plans to port to the RPi, however we may pursue that option when time permits. The CAN bit rate of the emissions CAN is the same as your Firefly/Spyder CAN, 250K.

  21. Daniel says:

    is there a way to get this to work with a raspberry pi?
    since all options are on back order?

    • Voltdoc says:

      Not right now, only the Arduino hardware specified is currently supported. There are no immediate plans to port to the RPi, however we may pursue that option when time permits.

  22. Roland says:

    I have purchased all the parts, but now the software will not run on my Windows 10 PC. Says “This app can’t run on your PC” To find the version for your PC, check with software publisher.

    I have tried different compatibility modes or running as Admin. Still no luck.

    • JWP says:

      Hi Roland, I will be glad to help you trouble shoot and get the software working for you. I have a couple of different ways that I can help. Lets start by direct email. Please check your in box for a email from me>

  23. JB says:

    If I get the correct connector, would this work on a Paccar PX9?

    • Sschevygrl says:

      Not sure about PX9, but we just installed Uno on PX7 in 2017 Kenworth T270 rollback and it appears to be working. DEF gauge went from “0” w/red light to 3/4 and after 3x of 5 min idle and restart all dash MILs are out. We did have a bit of extra figuring out on the plug because ours was a 4 pin spade, different color wires and different pin order, but once you find hot and ground, it’s a 50/50 chance on CAN L and CAN H. We had them backwards at first and the truck DEF gauge read “0”, as soon as we swapped the 2 wires, it worked like a champ!

      • Archer2 says:

        That is brand new, I think you are the very first PACCAR PX installation. If you have pictures of the actual connector as well as what color wires went where, if you could attach them or send them in an email to you might help others with KW PX engines.

  24. Walt says:

    The recommended supplier is out of stock on Dual CAN Bus Interface For Arduino Due With Extended Power Range. Is there other suppliers for this item?

  25. Francis McGuinness says:

    We full time in a 5h wheel/F350 diesel combination. Thankfully, we haven’t had this particular issue to deal with.
    That said, I am so impressed with the effort and cooperation that has gone into this project. My faith in the human spirit and American ingenuity has been verified (yet again).
    Safe travels everyone.
    We’re looking forward to seeing all you folks on the road again.
    Mack & Mary Ellen
    Somewhere, USA

  26. Marty Weston says:

    I just finished testing my DSS and it was a raging success! Thank you to all of those involved, I can’t convey how much all of your efforts are appreciated. As being the victim of a failed Def sensor while on the freeway enroute to a week long RV rally, I felt the frustration of being “out of control” to handle the situation. Not knowing if and when the rig would got to limp mode, or if I shut it off if it would ever start again. Your ingenuity will benefit untold numbers of fellow RV’ers. This device is priceless, ask my wife!

  27. Jerry Pate says:

    Looks like the CAN bus interface boards are sold out and they are not accepting orders at this time. Are there any second sources for the processor board with CAN bus interfaces. Thanks, Jerry 210921

  28. B Steelman says:

    Hello, thanks for this information. I have one question. Can the software be installed in the Arduino Due Board without the CAN Bus interface attached to it?

  29. Debbie Rackley says:

    I ordered all items last weekend and today I got the circuit board.

    I followed the instructions closely, the programming part was over in about 2 minutes from downloading the files to programming the Arduino board.

    The mechanical assembly was very straightforward, I mounted my circuit board on 3 small nylon spacers with retaining screws (size 4-40). Plan out the cable route and do remove a few strands from the V+ and Gnd wires. I had to drill a 3/4″ hole for the cable gland I had. I’m going to cable tie the emulator box to a frame member if I ever need to use it.

    I ran the Bus yesterday, so I knew we did not have any error codes. I connected the emulator, started the engine and let it run for about 5 minutes and got no error codes. Yippee! One pleasant surprise was our Allegro Bus is the first year of the glass dash and the dash showed the proper DEF fluid level and proper DEF temp when the engine was running.

    I shut the engine off and reconnected factory configuration and restarted. No error codes.

    I believe this is the best $150 I have spent in a long time. We leave in 2 days for a 2,500 mile 6 week trip so this provides a lot of peace of mind.

    Well done developers!!!!!!!

    Do you guys have a way where I can send you some “Thank You” money????????????

    • Archer2 says:

      No money required. We are just happy that you were able to get some peace of mind for your trip. If you frequent any of the RV boards and have the time, it would be great if you could relate your experience for the benefit of possibly those folks who would like to build a DSS but are not as confident in their ability to handle it.

  30. Jim Brant says:

    I had to get the Aduino-Duo.Core-B board because they were out of stock on the first board you had listed. I am trying to program the ECU and when I run the command it tells me No Device found on COM7. That is the COM Port it is attached to. What am I doing wrong?

    • Archer2 says:

      Hi Jim, I’m not 100% sure what board set you have but it looks like you are saying you have an Arduino DUE (not Duo)? Also the Due also requires a CANBUS shield. Can you tell me what CANBUS shield you have? But, as far as your problem, if you do have an Arduino DUE look carefully at the picture in the Quick Build section. The DUE has TWO USB connectors on the same end of the board that the power connector is on. You need to plug the USB cable from your computer into the USB port CLOSEST TO THE POWER connector. Then recheck what COM port your computer assigned to it as it will probably not be the same as before. Then retry loading the firmware.

  31. Jim Brant says:

    Thank you for responding and sorry about the miss print. I do have the Arduino DUE based ECU Development board with Two CAN Bus Ports. part number JCOM.DUE.CORE-B. This morning I plugged on the board using standard USB cable. the board showed up on Port 8. I opened up CMD promt and typed the command string. Got Message board was not found. I checked in the Device manager and it changed to Port 9 with a different name. So then I typed the command using DUE 9 and it completed the program process. I purchased 4 boards and had to do all of then the same way. Hopefully they are programmed correctly.

    • Archer2 says:

      Hi again Jim. I’m going to post here for the benefit of others who might have substituted the same board as you did. So, Jim got a slightly different DUE-based board than the one we used in the Quick-Build instructions. The one Jim got was a JCOM.DUE.CORE-B from Copperhill. It comes with only one USB port instead of 2. It comes with a cable that is a USB on one end but a 6-pin UART on the other. That cable and connector cannot be used for programming the Arduino, you should use the USB port with a standard USB cable.
      Here’s a link to the CH page for comparison

    • Archer2 says:

      I failed to make clear in the last post that the board Jim has should work just fine. There are just a couple of minor physical differences from the one in the instructions.

  32. Mathis Weatherall says:

    Hi. I’m interested in building the DEF simulator. Thank you! Will this work for my 2017 Newmar Dutch Star on Freightliner chassis?
    Or is this only for Spartan?

    • Archer2 says:

      Hi Mathis. The short answer is that, yes, if you have a Cummins engine using a CM2350 ECM then it should work fine. BUT it appears that most if not all Freightliner chassis use a different physical connector between the sensor and the wiring harness than the Deutsch DT-04 shown in the instructions. That’s not a showstopper but you would need to source the right connector (there is info in the Comments so just look for it) and then figure out which pin carries which signal (ie +12V, GND, CAN_H & CAN_L)as we have conflicting info from the documentation we’ve been able to see.

      • Ardis Almond says:

        On my 2014 Winnebago Itasca Ellipse on a Freightliner Chassis (built April 2013) my connector is a 6 pin flat connector, with the wires colored as pink, green, yellow, pink, (no wire), and black with white(?)stripe. There is obviously 5 wires here, not 4. What next?

        • Archer2 says:

          Hi Ardis. Two things here. The first thing is that sounds more like the connector that goes to the remote DEF gauge, not the connector that goes from the DEF header to the wiring harness. But second, and more important is that your year chassis does not appear to be one that has a high likelihood of failure. Before you go any further you need to contact Freightliner to determine if your DEF header has all three sensors (temp, level and quality) and does it use a J1939 data bus? If the answer to either of those questions is No then the DSS is probably not for you. Good luck.

  33. Chris Glaze says:

    Love this idea! Do you have a phone number I could contact? Thanks.
    2020 Dutchstar Freightliner Chassis

  34. Paul Murray says:

    This is the way the world should work! Funny that even without regulation creators foresight and the manufacturers spineless attempts to force a solution, American ingenuity is alive and all these manmade obstacles can be overcome when us engineering geeks put our heads together. I would hire these guys in a second! Problem solving at it’s finest!

    The “Regulators” and their enablers love their power over the populace and should be embarrased by a simple solution from the masses.

  35. Rob A says:

    Fantastic, thank you! Where will info and a link to the Mac install version be posted? Just keep checking back on the Quick Build page?


  36. Lionel Robert says:

    Thank you for all you have done on this project. Can i use 20 gauge tinned copper for the cable on the simulator or should I go with a heavier wire. What is the 12 volt load on the simulator.

    • Archer2 says:

      The total current draw at 12volts dc nominal should be less than 300mA or 0.30 amps. And yes 20 gauge wire will be fine and a lot easier to assemble especially if you are using a DB9 connector.

  37. Mark Weber says:

    Hello: I have a single seed studio CAN bus board and I also have a few Mega boards laying around. Can I use this set up? I will provide my own regulator for the 5 Volts. Looks like you included a couple of extra folders – one for DUE, one for MEGA and one for UNO so maybe I can install by changing the call?

    • Archer2 says:

      You absolutely can use a Seeed shield with a Mega2560. Just follow the same instructions on the website for the UNO (including cutting the P1 trace to disable the termination resistor). The command line to program should just use “atmega” (all lowercase) instead of “UNO” and add the correct COM port. It works exactly the same.

  38. Larry Brons says:

    I purchased the Arduino-Due-Based ECU Development Board With Two CAN Bus Ports. I read the comment about not using the included 6 pin usb cord. I have a micro USB cord from another device, will that work? I plugged it into the board and the other into my Windows 10 PC. It’s not showing up in the Device Manager window. I’m not too tech savvy, where do I go from here? When plugged in, it appears to power the circuit board.
    Thank you

  39. Joe Zinkel says:

    Wondering if you or anyone has experience with this on 2018 Cummins 340?
    When I Look at my DEF tank, the head is nothing like you show in your photo ( recessed into tank), and as such the plugs look different.
    There is a yellow/black 4-wire plug that comes from center of head area, not sure if this is the same
    Wire colors leaving plug are gray, yellow,black,green

    • Archer2 says:

      What is a Cummins 340? Is that a Motorhome? Do you have a picture?
      I’m kidding but what year, make and model of vehicle? What kind of chassis? Seriously, do you have pictures to show what you are talking about?

      • Joe Zinkel says:

        2018 Pace Arrow 38k with Freightliner Power Bridge

        Can Pic be attached somehow?

        • Archer2 says:

          If you can’t post a picture here then sent it via email to

        • Archer2 says:

          OK, you have a Cummins ISB 6.7 340HP and we know that it will work. The trick is to figure out the connector that FL used. The connector is a
          TE 1-418390-1, this part number is the harness-side female connector. The part number for the mating male connector is 1-703818-1. Here is a link to its catalog page. The first digit, the “1” is important because there are 4 versions and they are not interchangeable. They differ in the color of the insert and the first digit (1, 2, 3 or 4 in the first position). What we really need is for someone to figure out and post here the correct wiring info for the 4 pins.
          Here is a video showing how the connector is assembled

          • sevd says:

            Thanks for the FL connector (housing) info! I have to visually confirm if my 2017 Monaco Diplomat 43S (FL) has the same connectors listed. Then I’ll wait for someone to identify the wiring info for the 4 pins. I’ve ordered everything else I need (UNO+CAN version) except for the 14/4 cable. (I assume any automotive grade 14 guage/4wire cable is fine since I don’t need the DT4 connector for FL.) I got a little confused trying to find the correct connectors that must be crimped to the wires and inserted into the connector housing listed, as well as the special tool to unlock the housing if you need to remove an incorrectly placed connection. Oh, and hopefully I won’t need that special AMP crimping tool — #91337.

          • Archer2 says:

            This is a general response to clarify something about the suggested parts list. Some of the items were specified, not for any technical reason, but instead because the part was available and simplified the building of the unit. The cable/connector is a great example. The cables listed are just to avoid having to assemble your own 4-pin connector or solder extension wires to the pigtails. Not only is it not necessary to use 14 gauge wire for this, it’s not even desirable. The power needs for these devices is minuscule so if you have the chance to use smaller wire (like 20 gauge for instance) then go ahead and use it.
            Same can be said for the CopperHill Due with Dual CANBUS and extended power option. The reason it was specified was because it provided easy to assemble screw terminals for the CANBUS and power connection. The DUE was specified, not for any operational reason, but because that was what the screw terminal shield fits on. There is absolutely no disadvantage If you want to use an UNO with a CANBUS shield and assemble your own cables and connectors. It’s just a little harder to put together.

  40. Don Rackley says:

    2019 Tiffin motorhome here with 450 Cummins L9. We left Winslow AZ today and drove to Page (190 miles) with the DEF emulator connected. I did not get any strange readings on the dash (was really checking) and no MIL lights. My previous driveway test was about 5 minute duration.

    The DEF level read correctly on the glass dash as well as the DEF temp reading. I am convinced this emulator is a good.

    Well done guys!!

  41. Eric Gladding says:

    I have a 2017 American Revolution on a freightliner chassis with 450 Cummins. My tank connector is different. It is more square and post are flat. Do you have info on this connector?

  42. chris mooney says:

    trying to program an uno board and all I keep getting is an error message that the file is not found. can someone email me for some assistance

  43. B Steelman says:

    Hello, I have completed the simulator build and programming of the DUE board,both were successful. I am having an issue with with one parameter, the “DEF Quality Sensor Temperature”. It is reading 419*f. The “DEF tank temperature ” is reading 70*f. I have hooked up to 3 other vehicles with the same outcome. This is still giving an ecm debrate code. Did I miss something while programming? Thsnks

    • Vic Chanko says:

      Well that’s odd. What are you trying to connect to? Make, model, year, chassis manufacturer, engine info, ECM info.
      Also what hardware did you use UNO, DUE and CANBUS shield.

    • Vic Chanko says:

      Also, do you have the PGN/SPN numbers for the parameters that are out of specs? The DSS doesn’t send any data for “Quality Sensor Temperature” and that specific parameter description does not appear in the SAE J1939 standard that I can find.
      PS, I see you used a DUE. Is it the one from Copperhill that is in the instructions or is it something else? Does it have the Copperhill “Dual CANBUS with extended power” daughterboard?

      • B Steelman says:

        Yes, I am using the Copperhill board as listed in the build instructions. Vehicle application is an Eldorado Transit bus 2018 with an ISB 6.7 CM2350A. DEF unit is the Shaw Development unit, same as most coaches use. Fault codes 6255(Cummins)
        SPN 1569. All others went inactive related to DEF quality.

  44. john briese says:

    Thank you so much. Great peace of mind. Any comments on storing this for later use?

    • Archer2 says:

      Glad your project was a success. As far as comments on storing for future use, yes. Store it someplace where you will remember where you stored it!

  45. 5511564 Cummins def header sensor
    We have a Cummins Motor attached to a truck that needs a new DEF Header Sensor as noted above. Will this DEF Sensor simulator work for this application.
    Cummins telling us that it want be available for 100 days.

    • Archer2 says:

      We need a lot more info. Make, model of truck. What engine, which ECM and year the engine was actually built. Will Cummins not perform the emergency recalibration (in other words reprogram the ECM so as to disable the deration inducement in the case of a failed sensor?

  46. Steve Buckman says:

    Question – I’ve built two of these simulators, one of each model. I plugged both in and they appear to function. However, when I plugged the first unit in I had 3/4 tank of def and fluid temp was 72 degrees. The second one I had 1/3 tank of def and fluid temp was 80 degrees.
    Now when I plug either unit in it show what the initial values were when I first plugged them in, i.e. 3/4 tank for one unit and 1/3 tank for the other.
    Question is if my sensor fails and shows zero def and who knows what temp and quality defaults to on a failed circuit – what values will the simulators report to ecu when it’s plugged in?
    I hope this question makes sense to you.

    • Archer2 says:

      Steve, am I understanding that you have two different devices, one DUE-based with a Copperhill shield and one UNO-based with a Seeed shield. Correct? Second are you saying that you are testing them one at a time by connecting them to the EXACT SAME vehicle but getting a different reading on the main DEF level gauge BUT no other fault codes like “SPN 1761 FMI 9”? Does the vehicle have a good, functioning OEM sensor or did it have a failed one? What kind of vehicle is it? Make, model, year and type of engine?
      The reason this is really weird is that while the hardware may be different, the software is exactly the same. The output data from any DSS is identical to every other one. The DSS does not depend on or store any data or values whatsoever from the vehicle, they are output-only devices.
      My guess is that there is something wrong with the one that shows 1/3 full tank and 80 degrees. What I can’t figure out is how it is not functioning but also not causing any faults or warnings. You say that the boards both show that they have power (ie LEDs light up and flash) so we can assume that the +12v and ground is wired correctly (and if it weren’t you would get instant errors) so it only leave the CANBUS wires and if they were reversed you should also get faults. It’s a mystery! Can you contact me at to continue troubleshooting via email rather than using this website?

  47. Richard Mackenzie says:

    Building def simulator using uno board with a seeded can bus my question is about cutting the trace wire on the can bus how do I know it’s been cut is a way to test that it’s been cut

    • Archer2 says:

      If you have a multimeter that measures resistance either measure across the two P1 pads to verify that it doesn’t measure 0 ohms (a dead short) or you can measure between CAN-H and CAN_L. It should measure substantially higher resistance than 120 ohms. Or you could, of course, just use a magnifying lens and visually verify that the tiny little copper trace has been severed. It doesn’t take a whole lot of effort with an X-acto or a box cutter.

  48. Larry E Slate says:

    In comments ” Note: It may not be obvious, but the green part with the screws unplugs from the green part on the circuit board so go ahead and remove those connectors, it will be much easier to attach the wires.” Does the green part lift up or slide out? Is it the entire green piece or just the part with the screws?

    • Archer2 says:

      The green connectors may be separated for easier wiring. They separate at the seam just behind the screws. Hold the part of the connector that is soldered to the circuit board and pull the part with the screws gently away from it. You may have to wiggle the part with the screws back and forth gently to work it loose.

  49. Paul V Campbell says:

    Copperhill Technologies is now posting a long warning/disclaimer on their site relating to the use of their devices for a DSS. CYA to the max.

    • Archer2 says:

      We are aware of that. Copperhill posted that warning coincidentally at about the same time that they sold out of the boards and while they were at the same time scrambling to obtain more inventory. Perhaps the owner was trying to buy time to restock before customers looked for an alternate source. Who knows?
      In any case we obviously strongly disagree with the Copperhill assessment and believe that they mis-characterize the DSS by lumping it into the same category as “Emissions Delete Devices” which it absolutely is not.
      But, it’s their website and they can defend whether the warning is factual or not. We think it is not.

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