OBD diagnostic devices enable the rapid detection of malfunctions by reading out the vehicle’s own diagnostics. Thanks to constant further development, the prices for corresponding diagnostic devices have continued to fall in recent years, so that they have also become affordable for the hobby mechanic. In this guide, you will learn how an OBD scanner works and what you should consider before buying such a diagnostic device.

What is an OBD scanner?

An OBD scanner is a small diagnostic device with which you can read out error codes from the vehicle. Thanks to this fault diagnosis, defects in the car can be detected quickly and easily. For some years now, OBD scanners have been available as handy devices with which a diagnosis can be made directly on site.

If, for example, the check engine light in the vehicle cockpit is illuminated, the driver cannot see exactly what fault is present in the car. For fault diagnosis, the scanner is connected to the OBD port of the car. In most vehicles, the OBD port is located under a cover in the lower area of the dashboard or hidden in the centre console.

Vehicle diagnostics by means of OBD2

Modern vehicles have a built-in vehicle diagnostic system that monitors all installed sensors and control units and evaluates the corresponding data. This system is called on-board diagnostics or OBD for short. If malfunctions occur, a corresponding error code is stored in the car’s memory.

Originally, the OBD system was primarily used to detect any defects within the exhaust gas purification system. Later other OBD2 functions were added. While earlier systems only reported a malfunction via signal lamps or an error code in the on-board computer every newer OBD2 system has a diagnostic port.

This is the difference between OBD and OBD2

Before a uniform access to vehicle diagnostics was created with the modern OBD2 interface, manufacturer-specific systems already existed. However, these diagnostic facilities differed depending on the vehicle manufacturer and partly also on the model. The early systems are today referred to as OBD or OBD-1.

How modern OBD2 car diagnostic devices work

A modern OBD2 diagnostic device enables the readout of the fault memory in the car and thus a better diagnosis. In addition to scanning stored fault codes, many devices also allow stored faults to be deleted. The connection to the vehicle is very simple:

• Search OBD2 socket
• Connecting the diagnostic device
• Establish the connection
• Wait for diagnosis and error code
• Analyse error messages
• Clear error message if required

After connecting to the OBD2 port, the OBD2 diagnostic device reads out the data from the various control units. Subsequently, the faults found during the test are output graphically on the display of the device or on a smartphone connected to it. If a problem has already been corrected, the corresponding messages in the fault memory can be deleted.

Various diagnostic devices available

OBD2 diagnostic scanners are available in different versions. Many professional devices are connected to the vehicle via a diagnostic cable and have a built-in display. Less expensive devices sometimes have a USB cable or bluetooth that can be connected to a notebook or PC.

Other diagnostic devices simply consist of a small dongle that is inserted into the OBD2 socket of the vehicles. Here, the connection is made via Bluetooth or WiFi, whereby the data can be sent directly to a tablet or also to the smartphone. A current version of the required diagnostic tools can usually be downloaded directly as an app from the manufacturers’ websites.

Do I need an OBD scanner?

Good OBD2 scanners are not always cheap, and so the question sometimes arises as to whether the diagnostic device is needed at all. However, it makes sense to buy an OBD2 scanner, especially for modern cars. If, for example, the engine sounds unusual or warning lights light up in the vehicle cockpit, any fault codes can be read out quickly and easily.

For those who like to work on cars and carry out repairs themselves, the purchase of their own OBD scanner is imperative. For example, stored errors can be easily deleted with the device after a repair.

OBD2 diagnosis pays off quickly

With the diagnostic device all vehicle information can now be read out in the garage at home which saves unnecessary trips to the workshop. In addition, reading out the fault codes there costs at least 20 euros. So having your own diagnostic device pays for itself quickly.

The diagnostic device can also be of good service when buying a used car. Older vehicles in particular often have weaknesses and recurring faults. A short test using an OBD2 scanner can be useful here. As a rule, honest sellers do not object to prospective buyers subjecting the respective vehicles to a test using a diagnostic device.

Buying an OBD diagnostic device – what you should look out for

In the field of diagnostic devices, numerous different devices are offered by different manufacturers. It is therefore helpful to clarify your own needs in advance in order to be able to select the right diagnostic device.

1. Does the diagnostic device fit my car? – Not all car diagnostic devices can be used for all vehicles. Although most modern OBD2 devices can be used universally, the compatibility with your own car should be checked before purchasing.
2. What range of functions do I need? – The range of functions and diagnostic tools differs depending on the diagnostic device. Higher-quality devices usually offer greater diagnostic depth and can thus read out several of the car’s control units. Semi-professional devices not only allow you to delete errors, but also to recode the ECUs.
3. Should I buy a device with a display? – The market offers diagnostic devices with and without a display, as well as with and without a cable connection. Whether you prefer the wireless version with Bluetooth and software app or a device with cable and display is often a matter of taste. Sometimes the cable-connected diagnostic devices are more sturdily constructed and also impress in rough everyday workshop use.
4. How much should the device cost? – Before buying, you should think about how much money you want to spend on the car diagnostic device. Simple diagnostic devices are often available at a low price. These only cost in the low two-digit euro range. Diagnostic devices with more functions and professional devices, on the other hand, can cost several hundred euros.
5. What accessories are included? – When buying an OBD2 diagnostic device, you should also pay attention to the accessories. With high-quality devices, suitable connection cables, a manual and the required software are included in the scope of delivery.

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