USDM, JDM, EDM….ADM… What does it mean?

Such Markets (crop)
A common problem we often help costumers figure out is, what “Domestic Market” their car belongs to and how it affects their ability to purchase aftermarket parts. This is especially important for tuning because in many cases, the car will use various versions of software on the ECU or even different hardware for separate markets even if the year and model of the vehicle are the same. So I’ll lay down some basic definitions and ground rules that should help you understand how it all works.

**IMPORTANT NOTE** – This information is exclusively relevant to ECU Identification and Tuning. Many of the comments and “rules” will apply to all aspects of a cars origin but this article exists purely to help someone determine what ECU ROM is most likely to live on your car’s computer.

Understanding Domestic Markets

The Domestic Market, or DM, for a vehicle can generally be defined by two attributes:

  1. The ROM on the ECU
  2. The varied mechanical configurations of each car, based on region-specific needs and laws/regulations

What is a ROM?

A “ROM” is the file that a vehicle manufacturer develops using internal tools and software to manage the engine and other functional systems throughout the car. The ROM is stored on your car’s ECU (engine control unit) and essentially functions as the cars operating system…like Windows on your laptop. The ability to identify, modify, and reflash a ROM on a cars ECU is ultimately the foundation of modern tuning.

Are there mechanical differences across markets?
Maybe…sometimes the only difference between two cars of the same year, make, and model in different locations is the ROM version. Other times, cars will have varied mechanical components due to inconsistent regulations or consumer needs in each market. There can even be significant differences within a market. For example, a car in California will often have a different ROM compared to a car in Texas even though both are USDM cars. When that is true, it is usually because there are mechanical differences between the cars that must be accounted for by the engine calibration, which is identified by the ROM.

Your vehicles “Domestic Market” has nothing to do with where it was built or where the company is from.

I think this is the source behind 90% of the confusion and it stems from two misconceptions.

  •  Many people just assume that the “market” for a vehicle is based on the country of origin for the manufacturer. I.E. “My car is a Mazda, and Mazda is a Japanese company, so my car is a Japanese Domestic Market (JDM) car.” I can totally understand why someone might think that, but it’s not accurate. A BMW even if built in Germany is not necessarily a European Domestic Market Vehicle either. The same goes for any other brand, all Fords are not USDM. In general, the vehicle “market” is based on what country or region a car is going to be sold in. There is a lot more to it, but I’ll cover that later. 
  • The other source of misunderstanding simply comes from the enthusiast tuner culture using terms like “JDM” incorrectly. JDM and EDM are technical terms, not adjectives. They have a specific meaning and use, but the enthusiast community has adopted the terms and distorted their meaning. For example, people often refer to themselves as “JDM Car Enthusiasts” if they really like cars from Japanese manufacturers like Subaru, Honda, Toyota and so on. As I stated before, a car is only actually JDM if it was sold for the Japanese market, if your Nissan has a steering wheel on the left side of the car…it’s not JDM. Of course, there is generally nothing wrong with the way people use the term in a casual setting, but it does become a problem and source of confusion when a professional Tuner is trying to figure out what ROM to flash to your ECU but you tell him its a JDM car, when in reality, you bought the car in Ohio…so its a USDM car made or designed in Japan.

Every country or region does not have its own “Domestic Market”.

After reading this far, you might assume that the market for your car is basically just defined by where it was sold when new. That would be convenient but it’s far from the truth. That being said, it’s actually a good thing that this is not true because most cars only have a few unique configurations for the entire world instead of needing one for every single different county. Tuning would be a headache if that was the case.

Most Common Markets

There is no universal standard followed by all car manufacturers but there are some consistent trends or patterns that make things relatively easy to follow.  The majority of the cars in the world will fall under one of the following DMs.

USDM: Most ROMs/cars in North America will fall under the USDM designation. So the US and Canada are almost always the same. More often than not, that also includes cars in Mexico, but they do surprise us sometimes with cars from overseas markets.

JDM: These will be almost exclusive to Japan, but occasionally they will be found in various parts of Asia or Australia.

EDM: Often, all or most of Europe will share a standard ROM type or family of related ROMs. That includes the UK and they will pop up in other nearby non-overseas areas.

ADM: The Australian domestic market. Obviously, most of these cars will live in Australia, but we have seen a few ADM ROMs appear in other areas where RHD drive cars are common. Also, there are a decent number of JDM cars in Australia.

CHDM: Similar to JDM, these usually stay in China but will be found around Asia or even Australia.

MEDM (Gulf Spec): Many brands do no have this market, but some platforms have a specific Middle Eastern Domestic Market.

??????DM – The last “market” consists of several regions that tend to be a bit of a crap shoot. Areas like South or Central America and certain parts of Asia or Eastern Europe tend to be a mixed bag of ROMs/cars from various markets. So if you want to tune a car and live in one of those areas, you will need to do some research either with the tuner or a dealership to find out exactly what ROM is stored on the ECU. It is possible for cars in these areas to actually have their own unique ROM, but they are not consistent enough to ever be a safe assumption. Sometimes the only option is to simply plug in a device like an Accessport for a factory service tool to read the information from the car. Then, you will know exactly where to start with your modification process.

World Market: Some cars (often the German brands) take a global approach. With a few exceptions, every car sold is identical across the world mechanically. In some ways that makes things simple, but in others, it is actually more complex. The one-size-fits-all approach is good for production but in order to match a broad number of regional regulations and laws, they must create entire families of ROMs and each of those families have various editions, sometimes in the hundreds of variations.

Regarding tuning, the benefit is that if software is developed to tune an ECU for a WM car, then it will potentially work on any car anywhere in the world. There can be dozens of variations of ROMs that need to be identified in order for the software to recognize the vehicle, it can take a long time to track them all down. It is quite common for a customer to try to install a tune just to discover that they are the first person who has tried to use it with a unique ROM version…so the software has to be updated by the developer before it can flash to the ECU. Tuning WM cars allows for broad customer reach but produces an almost non-stop need to update.

ROMs on ROMs on ROMs!

An important detail to understand is that ROMs and Domestic Markets don’t exist in parallel. It is possible for a single ROM to exist in more than one market, while on the other hand, sometimes one market may have various ROMs.

As a result, the complexity for a tuning company to support certain cars in certain markets will also vary greatly. Some platforms can be supported by a relatively small number of ROMs across the world, while on the other hand, some manufacturers make dozens of tweaks to ROM editions that can even change throughout the ownership of a single car. If you have ever taken a relatively new car to a dealership for service, and they “update” the car as part of the process. Often, what that means is that they applied a new ROM to the ECU. Every time that happens, we have to be aware of the update and apply it to our software to properly communicate and recognize the vehicle.

How to find the correct ROM for your car when using an Accessport:

World Market cars are the biggest offenders of the “Lots of ROMs” dilemma. Luckily, when using an Accessport, it will do most of the hard work for you. Typically the Accessport will be able to recognize the ROM upon install and will automatically select the correct set of OTS maps that apply. But if you are getting a custom tune or if you need to redownload a COBB OTS Map from the website, you will need to know what ROM is on your car to make sure it matches the new download or base file that the ProTuner is making your map with. That is easy to do.

The Accessport will store the ROM information after it is installed to the car. You can find it at any time by following these steps:

screenshot5 screenshot6 Macan ROM
Select the “Help” menu on the
home screen.
Then select “About Accessport” The “Installed Vehicle” section will show
the ID for the last ROM applied to the ECU

Unsupported ROMs: What to do if the Accessport doesn’t recognize the ROM on your car

As mentioned before, it is possible for your car to be supported but not the ROM on the car. That situation will occur in one of a few ways:

  1. Your Accessport is on old Firmware…this happens all the time….CHECK FOR FIRMWARE UPDATES FIRST!  🙂 (Accessport Manager)
    How to update your Accessport. 
  2. The vehicle is new and we simply have not collected all of the ROMs in existence. (see below)
  3. Your car was recently updated at a dealership and they applied a new ROM and we may need to add support for that ROM. (see below)
  4. Unfortunately, your particular ROM is simply not supported and might never be. But all is not always lost, often all that really means is your car is on an old ROM and having a dealership update the car will solve the problem.
  5. Similar to #4, sometimes manufacturers release super rare ROMs or dealerships update cars incorrectly and the ROM is so rare that we do not support it. Again, this is usually resolved by having the car updated by a dealer or shop with the correct service tool.
  6. Lastly…it could just mean you have the wrong Accessport or your car is not supported at all. Double check the part number for your Accessport.

If #2 or #3 apply to you. Then you will need to contact us to help you out, but the first thing you need to do is retrieve the ROM from your car so you can provide it to us (most of the time you’ll discover we are already aware and are in the process of updating firmware).

Here is a simple guide for – How to Dump an Unknown ROM File

Finding the correct vehicle on the COBB website:

When shopping for parts on the COBB website, the easiest way to be sure you are purchasing items that will be compatible with your vehicle is by using the Vehicle Configure option at the top of the homepage. This same guide applies when trying to download OTS maps.

Just click “PRODUCTS”
GTR Select1(arrow)

Then enter the Year, Make, and Model
GTR Select2(arrowed)

The last drop down for “OPTIONS” will display all of the domestic markets that we support for your specific car. This is where you have to be very careful to select the appropriate choice. Many markets share the same parts but others do not, so if you select the incorrect option, you may accidentally order a part that is not compatible with your vehicle.

Once you select the correct market option, then click “FIND PRODUCTS” and the new page will automatically filter to only display items compatible with the selected market and vehicle.

Note: Unfortunately, we cannot always support every existing market for every car. Sometimes you may see that we provide parts or tuning for your make and model, but if your market is not listed, the parts may not work on your specific car.

If you ever have questions or need clarification please contact our support team:

Phone – 866-922-3059
Email [email protected]

If you are new to the tuning community, check out our COBB University Video Series to get up to speed!

35 responses to “USDM, JDM, EDM….ADM… What does it mean?”

  1. If I put the same engine in my car, but the engine I am swapping with is from Japan. Will this work with the cobb accessport?

    • Hi Nick,

      What exact car and engine are you expecting to combine? If it’s a Subaru, you have to keep the USDM ECU as we do not support the JDM cars. That also implies you may need to do some work with the heads etc because the JDM engines commonly used are the 2.0L that have AVCS but the older USDM ECU’s can’t control that, so it has to be disabled mechanically.


      • Hello. I replaced my USDM EJ255 with a JDM EJ205 in my 2014 WRX. ECU is still the USDM from what my mechanic told me. What is the best way to go about tuning my vehicle to boost performance. Can i go with the Cobb AP off the shelf tune?


        • Hi Jesse,

          Since the original ECU remained in the car you are able to use an Accessport for your 2014 WRX (AP3-SUB-003). Unfortunately, we aren’t going to have an OTS map that will support the JDM Engine as there are going to be some slight tuning differences. I would recommend reaching out to one of our Subaru Protuners to see if they may be able to help with a custom tune.


        • Hello, I have a 2009 2.5L USDM subaru wrx. My engine is a JDM EJV20X from Japan, but it is the same ECU (USDM). Honestly, the car is going really well with this set up. But, is it compatible with a cobb accessport? Thank you! I’m from Canada.

          • Hi Guillaume,

            The Accessport will be compatible with the ECU you are running. Whether there are difference that will require tuning changes with the engine you have is not something we’ve explored. I would not recommend using the OTS maps and instead getting a custom tune to be on the safe side.


    • Hi Steve,

      Thanks for asking but as it turns out we do not have plans for UK Subaru support at this time.


        • Hey Jack,

          We do not offer support for JDM ECUs, unfortunately. The Accessport would not be able to identify and install (required to used Gauges) on your ECU. Sorry for the bad news!


  2. Hi there,
    When you are configuring your vehicle, how do you know if it is a MT or an AT. I have a 2016 wrx and I want to buy an accessport, I just don’t know what options to pick.

    • Hi Mike,

      As it turns out, the Accessport is not compatible with JDM Subarus. Sorry for the bad news.


    • Hi Dennis,

      The Accessport will only communicate with an ECU. If you retain the USDM ECU, you should be able to at least install it. This isn’t something we’ve ever tested so you may run into compatibility issues.


  3. What will happen if I use a USDM with a ADM rom?

    As you guys don’t make a Stage 2 for ADM with Intake and TB exhaust for ADM???

    • Hey Adam, that unfortunately will not work. In general, an ECU’s operating system is vastly different across markets and changing the ROM is not feasible.


  4. Hey I have a 19 usdm wrx and I have a catted downpipe would would the adm stage 2 tune work or would I need a full custom tune?

  5. Hey Y’all. I bought my 2016 Ford Focus RS brand new in Canada at a ford dealership. It was built in Germany but sold in Canada. Is it a USDM or EDM? I need to know this before I order a Stage 2 Package from Cobb. Thanks

  6. Hey, i bought a used 2008 STi hatch 2.5L 6MT in Singapore. How do i know that it is ADM or USDM? Or could mine be JDM? Basically how do i check the make of the ecu? What are the best steps moving forward to be able to use the accessport on my car. As well as what part number shall i go for? Thanks.

    • Hi Faiz,

      Check out There are a few in Singapore. If you take your car by there, they will be able to plug in an Accessport and it will be able to tell if it is supported or not.


  7. Hi, I have ‘99 Subaru Impreza Outback that I’ve been planning on swapping to a jdm 2.0l sti engine. It came with the jdm ecu and 6sp transmission. I’ve read that I apparently can’t use the AP with the jdm ecu, but would it work if I stuck with the usdm ecu? Or would I perhaps be better off just getting an aftermarket ecu?

    • Hey Bryce,
      That’s correct, our Subaru Accessports do not support JDM ECUs that are often imported with their respective JDM motors. You can either stick with a USDM ECU (may require some custom wiring harness work – see iWire) or move to a full stand alone ECU (which would likely require a full custom harness).


  8. I have an USDM ecu and I have been able to upload OTS maps without any issues, I recently got a custom tune and the file says ADM instead of USDM. My AP won’t let me reflash the ECU due to it being locked to ADM. What can I do at this point to reflash my ECU?

    • Hey there, if your ECU is a USDM variant you will only be able to use maps for USDM ROMs. You would simply need to ask your Protuner to re-save the map to a USDM ECU type in order to use it.


    • Hey Kevin, you are not able to use a map intended for an ADM car on a USDM car as the ECU programming is different between the two.


  9. Thanks for shedding light on the fascinating world of automotive acronyms! The breakdown of USDM, JDM, EDM, and ADM is incredibly helpful for anyone navigating the diverse landscape of car modifications and imports. Your clear explanations make it easier for enthusiasts like me to understand the nuances and distinctions. Keep the informative content coming! 👍🚗

    • If you purchased the car in the United States or Canada, it is almost certainly a USDM vehicle. We see ADM ECU types in Australia and also other areas around Southern Asia.


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