OBD: On-board diagnosis briefly explained

You may be wondering what the abbreviation OBD means and are you interested in a few more technical details ?

In the following article we will briefly and concisely explain how OBD works, its history and why diagnostic technology plays an important role.

What is OBD?

The abbreviation OBD stands for “ On-Board Diagnosis ” and describes a vehicle diagnostic system that is used to monitor all exhaust gas-influencing systems of a vehicle, as well as other important control devices. Indicator lights can be used to indicate possible errors to drivers of cars, trucks or other types of vehicles. The data is constantly stored in the control unit and can be read out via the OBD interface .

The system differentiates between electrical diagnoses, sensor, actuator, system and component diagnoses. The task of an OBD with its adapters , sensors and interfaces is to ward off dangers and protect the environment . With on-board diagnostics , engine damage can be avoided because emergency running programs are activated as soon as errors, such as a cable break, occur.

Maintenance and repairs are made easier with the support of an OBD system , as the vehicle information read out simplifies troubleshooting and finding defective components. When you visit the car workshop, the specialist can use the OBD error codes to determine the error more precisely and solve the problem more quickly.

OBD-2

The second generation of the on-board diagnostic system is called OBD-2 , which has been in use in the USA since 1996 and mandatory in Europe since the early 2000s. The first OBD was introduced in 1988 and took place against a backdrop of growing environmental pollution.

In contrast to the first, the second generation of the OBD can monitor and save the data read out. Any errors that occur are recognized in good time and can be avoided. An OBD-2 adapter makes it possible to read out the special error codes that show exactly where an error occurred. Monitoring of all emissions-related and electronic systems is possible with OBD-2 .

The following values, among others, can be recorded via OBD-2 :

• Combustion values
• speed
• Fuel consumption
• Engine load
• Cooling water temperature
• number of revolutions
• current location
• Function of the lambda sensor
• current gear
• current outside temperature

If the car manufacturer supports it, the exhaust gas recirculation, the secondary air system and the tank ventilation system can also be analyzed.

How is vehicle diagnosis carried out?

The vehicle diagnosis via OBD-2 is implemented via the 16-pin OBD-2 socket in the vehicle. The interface works with the OBD-2 diagnostic protocol and the manufacturers' specific diagnostic protocols.

The CAN bus or the K-line is used as a physical port so that the OBD system can monitor the lambda sensor function, tank ventilation system, combustion misfires, catalytic converter efficiency, exhaust gas recirculation function and the function of the secondary air system.

All requests to the control unit consist of a mode and a data set (parameter ID - PID). Since OBD-2, a standard for PIDs has been in effect in selected areas. In the event of errors, the debounce counter starts, and if the error has not gone out before the end of the debounce time, the OBD system enters it into the error memory and activates the check engine light if necessary.

A permanent control of all emissions-relevant components is not possible because, as with the catalytic converter, certain operating conditions are initially necessary. Based on the readiness code , a scan tool can be used to read whether all components connected to the exhaust system have been detected by the on-board diagnosis or not. As part of an analysis of the engine management and emissions control system UMA, the readiness code is read out.

The electrical diagnosis registers a short circuit to ground, short circuit to battery, cable breaks and implausible voltages. The OBD sensor diagnoses include a plausibility diagnosis, adjustment diagnosis, gradient monitoring and a “stuck” diagnosis.

The actuator diagnostics check whether the actuator reacts to a control. System diagnostics check whether the source values ​​of a system are still within an acceptable range over a certain period of time when conditions change. The component diagnosis concerns components that are not part of the sensor system and have their own sensor system. Examples include tank leak diagnosis and catalytic converter diagnosis.

Diagnostic software

Reading out certain values ​​from an OBD can be done with programs on a notebook or with apps . The connected computer transmits the necessary commands to the desired control unit via the OBD interface .

The control device is activated with its specific address and then the results are sent as a response. Commands are available for reading the control unit ID, reading and resetting the error entries, reading out the measured value blocks, testing and entering adaptation channels, as well as directly reading and writing memory cells.

An Apple iPhone or Android smartphone uses YUKAtrack as diagnostic software, for example, which can read and evaluate the OBD interface wirelessly via an OBD adapter .

Every vehicle manufactured after 2004 has such an OBD interface , which allows you to read out the values ​​recorded by sensors. The on-board computer of modern cars and commercial vehicles indicates errors that occur with indicator lights in red or yellow.

OBD GPS tracker

An example of a special OBD adapter is the OBD GPS tracker from YUKAtrack . This has a permanently installed SIM card, with which the real-time location data can be transmitted throughout Europe.

The OBD GPS tracker does not require any complicated installation as it is simply plugged into the OBD-2 interface . This offers reverse polarity protection and can be used flexibly.

There is also an integrated battery in the adapter developed specifically for vehicles. This means that the GPS tracker can continue to transmit location data if it is no longer connected to the OBD-2 interface .

Conclusion and future of on-board diagnosis (OBD)

This now rather technical digression makes it clear: behind the simple abbreviation OBD there is a lot of electronics and sensors that are installed in modern vehicles.

The on-board diagnosis takes on the very important task of continuously monitoring these systems and informing the driver in the event of a fault or, if necessary, immediately activating emergency running programs to ensure safety.

With appropriate software, the recorded values ​​and stored error codes of the OBD system can be read out in detail.
Special OBD adapters , such as an OBD GPS tracker , enable the desired data to be transferred very easily via the OBD interface , for example directly into an app.

OBD-3 , the possible successor to OBD-2 , would be the third generation of on-board diagnostics , which is intended to transmit certain error codes directly to the responsible authority via radio and thus ensure timely troubleshooting.