ELM327 adapter. Connecting and setting

Affiliate Disclaimer

Please note that some links on autozaycev.com are affiliate links. We may receive commissions at no additional cost to you if you follow our links and make a purchase from one of our partners.

Privacy PolicyAffiliate Disclaimer
ELM 327
  • Blog / 
  • Reviews / 
  • ELM327 adapter. Connecting and setting

The purpose of this article is to help car owners to overcome uncertainty regarding the use of the ELM327 scanner. The reason for the uncertainty may be the ambiguous and not always accurate description of the functionality of this device on the vast expanses of the Internet. Therefore we will talk in detail about what kind of device it is, how to choose a good scanner and what applications are better to use to get the maximum effect.

What is ELM327

First of all, let's clarify what we're talking about. We are talking about the ELM327 scanner, which can be found under the name ELM327 adapter or ELM327 scanner-adapter. These are all the same device, working through the OBDII protocol, and most often constructed based on the controller from the company ELM.

In fact, the name ELM327 has become a nickname and refers to all kinds of budget scanners that work with OBD2 and are similar in design and functionality. 

The ELM327 adapter is the most useful device for the car and the best way to prevent an early heart attack in the driver. It is a faithful helper and advisor that will help find the fault, which is half of the repair, and prevent an emergency situation. Based on the information from the adapter, many drivers will find it easier to decide to troubleshoot with their own hands and significantly save on car service.

Moreover, the cost of the ELM327 is many times lower than the basic diagnosis at the service station, so in the long run it is a purchase that is sure to pay for itself.

People's choice

Budget car scanner

OBD2 diagnostic adapter that works with iOS and Android smartphones

Adapter manufacturer and design

Like the vast majority of modern gadgets, the design of the adapter is the main and several auxiliary chips, which are placed in the case and provided with connecting elements in the form of conductors and connectors.

The most famous variant of the adapter is developed on the basis of the PIC18F2480 chip, for which the firmware was created by the Canadian company ELM Electronics. Exactly this controller is called ELM327. Its task is to convert the OBD protocol to the COM port, which we will talk about later.


It should be noted that ELM327 is not the only controller from the above-mentioned company, but it covers the largest number of protocols. The popularity of the controller is due to this factor. At the moment there are also more recent circuits (ELM 329), but working exclusively with modern protocols, for example, ISO 15765-4 (CAN).

ISO 9141-2
ISO 14230-4 (slow)
ISO 14230-4 (fast)
ISO 15765-4 (CAN)
KW1281 (SAE J2818)
SAE J1939 (250kbps)
SAE J1939 (500kbps)
SAE J1708 (J1587)
SAE J1708 (J1922)

Now two more ELM327 interpreters are available, namely ELM327 v1.3a and ELM327L, repeating the functionality of the standard integrated circuit, but working at low voltage.

You can see a clear difference in the operation of the controllers in the table:

Operating voltage4.5В - 5.5V4.2В - 5.5V2,0В - 5,5V
Low power mode (sleep)
Saving settings on waking up
RS232 Transmit buffer (Bytes)2565122048
AT Commands100144144
Check the CAN frequency during the automatic protocol search
Response pending (7F xx 78) Support

It is clear that one ELM327 controller is not enough to make a complete diagnostic adapter, so additional elements are needed. Most often these elements are: printed circuit board and housing, power, the harness for all data buses, and of course the converter from UART to USB, Bluetooth or Wi-Fi.

A schematic of a working OBD2 scanner might look something like this:

Diagram of a working OBD2 adapter

Depending on the converter that outputs the information to the user's device, there are three interface options on the market:

  • Bluetooth - the most common and budget-friendly models. They work with Android smartphones and laptops. The iPhone/iPad technology only supports Bluetooth LE (4.0) adapters;
  • Wi-Fi - universal and the most expensive. Compatible with Android and iOS smartphones and computers;
  • USB is an average version. Work only with computers.

Technical Specifications

The characteristics of the ELM 327 adapter itself are not as important to the average car owner as the devices it works with. And here we are happy to hear that the scanner is absolutely not demanding. Most often the software is supported by any devices with more than 16 MB RAM. 

But I will still note a couple of characteristics that may affect the stable operation of the gadget in your car. The operating voltage of the ELM327 is 12 V and the quiescent current is 45 mA. The weight of the adapter depends on the manufacturer, but more often it ranges around 50g. Finally, I recommend paying attention to the form factor of the adapter and the type of OBD2 connector in your car. Sometimes the box is wider than the access to the diagnostic connector, so the scanner does not connect or falls out.     

The advantages of the device

The main advantage of the adapter can be considered its affordability, simplicity of the device and ease of operation. The design, consisting of a single mass-produced microcontroller multiplied by millions of copies, has greatly reduced the cost and made the scanner accessible to all car owners.

A decisive factor in the popularity of the ELM327 is its extensive functionality. Among the most popular functions are the following:

  • decoding and clearing of diagnostic error codes;
  • monitoring the temperature of all operating fluids;
  • measuring the pressure in the fuel system;
  • throttle position.

Firmware version and command support

Currently, the original firmware has version v 2.3, but it is not yet widespread. So let's focus on those models, which are available in almost every car store or Aliexpress. They have proven themselves perfectly and are minimally different from the latest version.

Firmware v 1.5

By this version we will mean adapters built on the basis of a quality Chinese copy of the ELM327 controller. It happened on the controller version 1.4b, so this is the version of the official scanners available on the network. Since then, this firmware has become the most stable and best proven in the market of automotive diagnostics.

ELM 327 v1.5

Despite the large number of good copies, the Chinese wanted to cheapen production, so some scanners with this firmware may not work properly. That's why a little later I will tell you how to check if the ELM327 is working properly, so you won't be cheated by dishonest sellers. 

Firmware v 2.1

This firmware is in no way related to the original 2.1 controller firmware from ELM Electronics. Version 2.1 appeared due to the desire of the Chinese to make the production even cheaper and to fit the product to a certain pool of technology. It lacks the adequate work with many AT commands. Also the module is designed for commands not exceeding 2 bytes, so it can often distort the data or not function at all.

elm327 identifier result

Currently, the market is a mess with the firmware versions, as some sellers disguise v2.1 firmware as v1.5. Therefore, I recommend buying brand scanners that work on their branded chips.

Which ELM327 adapter should I choose?

We have already realized that not all devices have a good reputation, so I want to talk about those that were worthy in the tests. 

Let's start with the price of the device. The original can not cost less than 15-20 dollars. All penny options are copies, which with high probability will not function properly. It is better to spend once for a good diagnostic scanner and thus save yourself time, nerves and often money.

Now let's talk about brands that have earned their reputation over the years.


Brand of Shenzhen Chaoyue Technology Development Co., Ltd. operating since 2009. Engaged in the production and sale of automotive products: diagnostics, TPMS, etc. The first and second versions of the scanners are available for purchase:

Reliable scanner

Quality ELM 327 scanner

Brand diagnostic tool from the Chinese manufacturer Viecar. Works on BT4.0 protocol

New version

Compact scanner in a hard case

Updated version of Viecar OBD2 diagnostic tool with BT4.0 and USB Type-C support


Trademark of PRC Shenzhen city car Broadcom Technology Co. Ltd. It is engaged in manufacturing diagnostic tools for cars. Popularly used adapters iCar2 and iCar Pro. Pro version has support for Bluetooth 4.0, so they are fully suitable for use with iPhone. The body of the devices is made of durable solid plastic. The iCar2 version has an on and off button.

Good choice

Small OBD2 scanner

Compact diagnostic tool with power button. Works with Android via BT3.0

Popular Version

The top version of Vgate

Multifunctional scanner with support for Android and iOS devices. Top of the line iCar

A powerful scanner from an American manufacturer. The high quality of the device is accompanied by a high price. Works perfectly with multimode programs. Gives the maximum functionality available through the OBD2 protocol. Suitable for Android and iOS.

TOP scanner

The best ELM327 adapter

The most functional diagnostic scanner of the ELM327 line of analogues

Checking the originality of the ELM327 adapter

There are several ways to verify the authenticity of an adapter. A common option is to use the software.

The most famous at the moment can be called ELM327 Identifier. The essence of the program is to send 114 AT commands to the scanner, in order to determine its version and performance in general. Algorithm of actions is as follows:

  1. Connect the ELM327 adapter to the OBDII connector.
    Подключенный ELM327 адаптер
  2. Configure your smartphone, computer or tablet to pair with the diagnostic scanner via Wi-Fi or Bluetooth.
  3. Open the ELM327 Identifier and press the desired button with the pairing type.
  4. Wait for the program to scan the ELM327.
    elm327 identifier scan running
  5. Study the commands that our adapter does or does not support. Determine the version of the adapter and its capabilities.
    elm327 identifier result
  6. Read the details of the commands or restart the scan.

In the same way you can check the autoscanner with the OBDMax program.

Under the second option is the testing of all pins of the adapter with a multimeter. Connect the common ground to pins 4 and 5, apply power to pin 16 and look at the voltage on the pins. On pins 7 and 15 the voltage should be 11 V, on pins 6 and 14 - 2,5 V.

Another suggestion is to remove the adapter cover and make sure that there is a "correct" chip PIC18F25K80 and not a cut-down one, for example BK3231Q. The disadvantage is that we damage the appearance of the scanner, and it is not possible to return it to the store. So it is better to clarify the model of the controller in advance and ask for a photo from the seller, especially if you buy ELM327 from Aliexpress.


ELM327 compatibility with car brands

There are practically no problems in this regard. A quality scanner works with all vehicles that have been manufactured since 1996. The only condition is that they must be equipped with a 16-pin connector that supports the OBD-II protocol.

Разъем OBD2

For some cars, you have to buy a special adapter. The most common adapters are VAG 2x2 and GM12, but there are also more specific variants, for example, for Fiat, Alfa Romeo, Lancia, Chery.

How the ELM327 adapter works

The ELM327 vehicle diagnostic process consists of several logical steps, each of which we will explain in detail so that you have no questions.


The process of connecting the adapter to the car is reduced to installing the device in the area where the OBD-II connector is located.

The location of the connector depends on your vehicle. Most often it is on the left or right side under the steering column. Also the OBD2 can be located under or directly in the glove compartment. In some cars, like the Volga, the connector is located under the hood. If you can't find the connector, check your car's repair and operating manual or simply google the answer to this question.

The OBDII protocol is universal and supported by all modern automobile manufacturers. It consists of 16 pins, each of which has a fixed functionality or flexible, adjustable as needed by the factory.

Пины OBD2

Let us designate only the important pins that affect the operation and diagnostic quality of the ELM327:

  • 16 pin - Power supply (+12 V);
  • Pins 4 and 5 - Power and signal ground;
  • 2 and 10 pin - J1850 protocol with PWM (Mazda, Ford, Jaguar) and VPW (Chrysler, GM) types;
  • 6 and 14 pin - ISO 15765 CAN (CAN High and CAN Low);
  • Pins 7 and 15 - Protocol ISO 9141-2 or ISO 14230-4 (K-line and L-line).
OBD2 connector pinout

The information is transmitted from the vehicle units to the adapter, where it is converted. We need to get the data, which will be understandable to a specialist. Because of the age of the OBD2 protocol, the conversion takes place in two stages. First to UART (at the time of the protocol creation it was a COM-port) and then to the familiar to us USB, Bluetooth or Wi-Fi.


After connecting the adapter to the vehicle, you need to pair the devices. To do this, turn on the ignition and connect the scanner to your smartphone, tablet or laptop. After activating Bluetooth or Wi-Fi (depending on the auto scanner model), wait for the gadget to detect nearby devices. From the connections found, select the ELM327 adapter. It can also be detected under the name OBDII. Connect to it using the codes 0000 or 1234.


Now is the time to make the adapter settings. When you turn on the device, the adapter type should be detected automatically. Otherwise, you need to open the application settings and specify the type of connection (Bluetooth, Wi-Fi or USB). 

The adapter screen will now display vehicle information, gauges and indicators. In some applications, you may be asked to create a car profile. It is not difficult: just select your model from the list and mark its specifications.

How to connect the ELM327 adapter to a laptop

First, you need to connect the connectors OBDII adapter and the car. On the laptop go to "Control Panel" and select "Bluetooth Devices", and then click "Add". You will see a window of the Bluetooth connection wizard. Make sure that the box "Device is connected and ready for discovery" is checked and click "Next".

In a new window, a device named CHX or OBDII should appear. Choose, press "Next". In the next window, you must enter the PIN code for pairing. Usually it is "0000" or "1234" (unless the adapter documentation says otherwise). The setup completion screen will show the outgoing and incoming COM ports. Make a note of the outgoing one. This will need to be entered into the diagnostic program. This completes the connection.

Turn on the ignition, start the engine, press "Connect".

ELM327 software for Android and iOS

Mass application of the scanner for car diagnostics, has led to the emergence of a large number of programs. There is a separate range of software that is fully automated. Their installation and use does not present any problems. But it should be understood that all software is divided into two types.

Multimarque, which allows you to read information only about the units that are related to emissions. This is due to the history of the OBD protocol, which was created directly to control the emission of cars with internal combustion engine.

Specialized programs, customized for a particular make or model of car. They allow you not only to read a large pool of data, but also to prescribe certain information in the blocks of the car.

It is enough to go to Play Market to find and download free software for Android smartphones and AppStore for iOS users. From the variety of offers you can choose the most suitable option. For my part, I can recommend programs that have been tested by many consumers:

Torque PRO. Paid application. Has one of the widest functionalities among the OBD2 programs. There is a free Torque Lite cut version.


OBD Auto Doctor. A free multimarque application in English.

OpenDiag / OpenDiag Mobile. Free dealer software for ZAZ, GAZ, VAZ, UAZ cars.

OpenDiag connecting

Motor Data OBD. Powerful multimode application, with the ability to buy additional plug-ins for specific blocks or car models.

Car Scanner. It's not a bad free Russian app with in-app purchases.

ScanMaster Lite. Partially free app with multi-language support.

The software listed above continues to evolve, as evidenced by regular updates and additions. It should be noted that the adapter can come with its own software, which can also be used for its intended purpose.

For maximum efficiency of the ELM327 adapter, try to find the model application for your car, and only then turn to the multimode programs.

I would also like to mention that there are special scripts, most often written in Phyton, which allow you to reach even more blocks. But I deliberately do not talk about them in detail, because they carry the risk of systems failure, without the possibility of return. Therefore, only specialists should work with them.


As you can see, in spite of its simplicity and cost, the ELM327 adapter is an indispensable assistant for any car owner. Without wasting any extra time or money, you can make an initial diagnosis and determine the problem without a trip to the service station. The main thing is to choose the model and application wisely. 


Rate this article please

rated: 4