Many who have already read out error codes and encoded smartly will know that you need a so-called OBD-2 adapter. However, only a small part of the OBD-2 adapters available on the market can really encode. Most OBD adapters can only read simple error codes. But do you know what he is responsible for? We will educate you on this subject today!

So, what is an OBD2 plug? With the help of an OBD-2 plug, you can connect your vehicle to an external device (such as your mobile phone or laptop) to read out error codes or recode the car. OBD means on-board diagnostics and is an international standard for all vehicles. There is a corresponding 16-pin socket in the car. You can often find them in the passenger area next to the steering column.

In the next paragraphs we will show you what you can do with it and how this OBD-2 plug actually works.

The OBD2 Standard

After each manufacturer used to have its own system, the OBD-2 standard (Regulation No 715/20072001) for petrol engines was introduced in Europe in 2001 and for diesel vehicles in 2004. In America, on the other hand, all vehicles have been equipped with them since 1988. In Europe, the exact specifications are set out in standard SAE J2012 or ISO standard 15031-6.

The On-Board-Diagnose has been designed in particular for the monitoring of emission-relevant data. Thus, the efficiency of the catalyst, the function of the lambda probe or even combustion dropouts is monitored. Overall, however, OBD can read, monitor and process all the control units of the vehicle. These can quickly reach around 100 in newer vehicles.

The ISO 15031-5 standard

In order to standardise communication between a vehicle and an external diagnostic device, this international DIN has been

standard. Among other things, this regulates the query of at least 135 parameter IDs, the query of freeze frame data, the query of values of the lambda probe, the query of vehicle information such as chassis number and much more.

The socket in the vehicle

The OBD socket in the vehicle (female) has 16 cans. Of these, seven are reserved for manufacturer-specific purposes and continue to have no relevance for the OBD. The nine cans marked in red are assigned precise functions in detail.

Female 10 (as an example) explained in more detail

As an example for all other outputs, we explain socket/port 10 in a little more detail below. Basically, the port can be used in two different bit encodings. Ford uses pulse width modulation (PWM at 41.6 kbps), while GM, Chrysler, Toyota, and others use the pulse width modulation variable (VPW at 10.4 kbps). What they have in common is that 0 to 8 bytes of payload data can be sent per message, the maximum length can be 101 bits and the bus access is CSMA/CA. PWM works with a two-wire data line, while VPW has only one wire. In addition, different signal levels are used.

Read car OBD2

The OBD Adapter/Plug

If it is an OBD connector connected to a cable (pictured left), it is rather small and has no special features. If, on the other hand, it is rather an adapter without a cable connection, it is a box (in the picture on the right) in which, in addition to the plug, the technology for Bluetooth and/or Wi-Fi is housed.

The choice of plugs and adapters is unmanageable. Some adapters and cables are universally applicable. Others, on the other hand, have been specially developed for a manufacturer. The use of the ELM 327 chip is common to all.

The ELM 327

The ELM 327 chip is the actual “brain” of the plug. It is located in each plug or adapter. This advanced chip can read CAN protocols necessary for communication between a terminal device and the CONTROL units in the vehicle. The chip translates the vehicle data and outputs it in such a way that external diagnostic devices and software can read this data. The chip supports high-speed communication between the components and consumes very little energy at rest. In addition, it can be adapted according to the task.

CAN protocols (bus system)

In order to reduce the length of the harness in a vehicle (which could well contain up to 2km of cables) and thus save costs and time, a bus system for communication in all vehicles was introduced. You really have to imagine it exactly like a normal bus. It travels back and forth between two or more participants and transports information. The bus used in vehicles (CAN-Bus – Controller Area Network) processes the data requests one after the other. However, it is so fast that there are practically no delays.

The path of data

Suppose you want to know what your exhaust emissions are. The external diagnostic device or the Diagnostics app retrieves the desired data.

The OBD-2 adapter, which is located in the OBD socket of the vehicle, receives the request via Bluetooth or Wlan. The integrated ELM 327 chip translates the data into a language that the vehicle/CAN bus can understand. The bus now knows where to take the request, namely the control unit that is responsible for the exhaust gas values. The control unit receives the request and provides the desired information. A bus brings the data back to the OBD-2 adapter, where the ELM 327 chip translates the data again. Via Bluetooth, the data returns to the app or the external diagnostic device, where it is displayed graphically or in plain text. All of this happens within seconds or fractions of it.

Default values that can be retrieved via OBD2

With the help of the OBD-2 connector or adapter, a variety of values can be read out. What is possible is determined on the one hand by the manufacturers and on the other hand by the possibilities of the app/external diagnostic device. Real-time data can also be provided with many apps. Common values are e.g.

  • Engine load in %
  • Cooling water temperature in °C
  • Speed in rpm
  • Fuel consumption in l/100km
  • Location
  • and much more

Diagnosis apps in use

You can’t do anything with an OBD plug alone. It only serves as a connection between an app or an external diagnostic device and the vehicle. So we would like to introduce you to three apps that we are very convinced of and which we have chosen as our three winners in an earlier test.

1st place: Carly App

The Carly app convinced us completely and therefore became our test winner. With all the many functions, the clear and simple menu navigation is a real treat. This way, you always keep an overview. There is a universal app that allows you to read the error codes from several different car brands and perform other useful functions. In addition to reading out the error codes, you can query the “health status” of your vehicle, get real-time data and recode many features. The app has already been installed over 1,000,000.

Carly Car Read OBD2

2nd place: Carista OBD 2

Also our place 2 is not from bad parents. In addition to a full version, the app can first be tested as a free basic version. The menu can be customized. With over 500,000 installations a real favorite among users. Unfortunately, there is a catch: the reading of real-time data is not possible and therefore for many perhaps a knockout criterion.

3rd place: Torque Pro OBD 2 Car

Torque Pro takes third place with its huge range of functions. In addition to the well-known basic functions, these are in particular the real-time data analysis, the head-up display mode, the dynometer and the GPS/OBD speedometer incl. Tracking option. The data can be uploaded to the provider’s server, sent by e-mail or saved as a CSV file.

Big Brother is watching you

Here is a glimpse of a possible future … the OBD-3 standard. Once again, OBD was introduced to monitor emission-relevant systems. Certain exhaust gas values should not be exceeded and thus the environment should be spared. If OBD-2 detects an error, you will be informed in the form of a warning lamp or error codes. But nothing more. It is up to you whether you go directly to a workshop or not. If your next AU is only in 12 months, you will just continue to drive around with the raised values.

Not so with OBD-3! If an inflated value occurs, a corresponding notification to the competent authority is automatically sent (WLAN/Satellite/SIM card). Now you have a certain time frame to have the error corrected, otherwise fines are threatened. The U.S. is already quite far in developing this standard … whether and when it will be introduced in Europe is completely open.