What is OBD

What is OBD? Understanding On-Board Diagnostics System

One of the major disturbing things about driving is seeing the check engine light come on. Many drivers are very familiar with the lights and indicators on their dashboards. However, they get frustrated because they know it’s a sign of another car problem.

Nevertheless, these lights are crucial as they are the surface-level indicators for a complex system of diagnostic signals that invariably work to tackle a car’s health. Whether it’s on a personal vehicle or commercial vehicle, these systems, also referred to as OBD2 scanning systems, are now a standard, making vehicle diagnosis and maintenance very straightforward.

What is OBD?

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So how the OBD2 system works? OBD or On-Board Diagnostics is a system in the engine’s onboard computer that tracks the performance of almost every emission-related part for malfunctions. The computer system gathers data from the network of sensors inside the car, which the system can use to regulate car systems or alert the user to problems. A technician or mechanic can then plug into the OBD system to gather vehicle information and diagnose the issue.

Why was OBD developed?

The history of OBDs started in the 1980s. During this period, vehicle monitoring systems were created in reaction to several factors, which include:

  • Emissions control

One of the main reasons for designing OBD was to reduce vehicle emissions. OBD systems are key in this area as they track vital engine parts’ performance for any system failure that could lead to heightened emissions. It can be tested via an O2 emission test sensor.

  • Electronic fuel injections

After the first electronic fuel injection system was installed on the 1967 Volkswagen 1600, many automakers started to feature it on their vehicles in the 1980s. Unlike the mechanical fuel injection systems, electronic fuel injection functions through computer control, with the computer system monitoring and determining the flow of fuel into the engine.

  • Electronic parts

With the electronic fuel injection system’s popularity, more electronics parts have become a staple in most cars. As a result, it increased the need for more advanced monitoring systems to detect issues more precisely.

Since its discovery, vehicle monitoring systems have undergone lots of changes. Currently, the OBD serves as a standardized system that decides the connectors and trouble codes utilized, making it simple for technicians to service a broad range of vehicles fast and precisely.

Related article: How to locate OBDII Port easily?

OBD History

The OBD system’s evolution can be split into two different phases based on the kind of system popular at the time. These are as follows:


The first OBD systems were proprietary; hence they differed between manufacturers. Before 1990, the codes, systems, and information collected by every OBD system differed broadly from one manufacturer to another.

Even though the OBD1 vehicle scanning systems were critical, they were highly complicated for technicians to work with. This is because technicians had to buy a new tool and cable for every vehicle, or they were forced to acquire a scan tool that featured different adapter cables for different vehicles. As a result of these systems’ proprietary nature, users were normally forced to go to dealership technicians to diagnose various problems.

The campaign to standardize OBD systems didn’t begin until the California Air Resources Board authorized OBD capability in all vehicles in 1991. The board never issued any standards for these OBDs, but it led to increased difficulties for car manufacturers and users. When the OBD2 standard was enforced in 1994 in response to this need, all former OBDs were classified as OBD I systems.


The California Air Resources Board issued OBD2 as a set of OBD systems standards for all cars in California, in 1994. This standard was formally applied in the 1996 model year and has been in use from then onwards. Additionally, the Society of Automotive Engineers and the International Standardization Organization referred to as the SAE and ISO, respectively, as well as issued standards for how digital information should be interchanged between ECUs and a scanner. Additionally, the EPA further expanded the use of OBD2 after the passage of the Clean Air Act to ensure that they match emission standards, and OBD2 is an essential part of these inspections.

With these two systems in place, technicians can service a broader range of vehicles, which is very fast and straightforward.  

How has the OBD changed over the years?

Since its introduction in the 1980s, OBD has changed a lot over the years. Earlier, the system would inform the user that there was a challenge using the MIL but wouldn’t keep any data according to the issue’s nature. As vehicles become more sophisticated, the number of sensors set up in cars increased, as did the information kept inside the system.

How does OBD work?

A basic OBD system comes with a central system, a network of sensors, indicators, and a connection point, making a complete monitoring system with standardized access and readability. The OBD system features these parts:

Related article: How you can understand OBD2 freeze frame data easily?

ECU – the central section of the OBD system is the Electronic Control Unit, also referred to as ECU. The ECU gathers input from different sensors within the vehicle. Later on, it uses this information to either monitor for problems, or control parts of the cars, such as fuel injectors.

Sensors – sensors can be found all over the vehicle – from the engine and the chassis to the electronic system. Every system sends codes to the ECU, defining the source and the parameters of the signal. The ECU then reads and interprets these signals.

DTC – When a sensor sends information to the ECU that falls outside of the usual range, then the ECU saves the information as a code referred to as Diagnostic Trouble Code or DTC. Basically, the DTC code is a list of letters and numbers that show the issue’s source and nature.  

MIL – After the ECU gathers a DTC code, it sends a signal to the vehicle’s dashboard to turn on the right indicator light.  These lights are referred to as Malfunction Indicator Lights or MILs, and they give an early warning system for vehicle problems. Note that if the light turns on and stays on, the issue is minor. But if the light flashes, the issue is significant and has to be handled right away.

DLC – All of the information and DTCs gathered by the ECU can be accessed through the Diagnostic Link Connector or DLC. Note that the DLC is the point of access for vehicles with professional OBD systems and is usually located below the dashboard on the driver’s side of the car. Nonetheless, it can be situated somewhere else in commercial vehicles.

What can I use the OBD for?

On-Board Diagnostic tools can diagnose a wide range of vehicle problems. Furthermore, their work has expanded and includes doing more than just detecting issues with your vehicle. Additional OBD uses include:

  • Emission testing – OBD2 testing is now a usual way of testing vehicles for emissions in states of the U.S that needs it. As a result, drivers can quickly know if their vehicles are compliant with emissions or not.
  • Driver behavior monitoring – most automotive-related industries have continued to use OBD systems as a method of tracking driver behavior.
  • Commercial vehicles telematics – commercial vehicle companies typically utilize what is known as Generic OBD2 to collect data about their fleet. This includes fuel efficiency tracking, remote diagnostics, fleet monitoring, driver behavior monitoring, and much more.  


 Now that you know what OBD is and its benefits, ensure to acquire a suitable OBD2 scanner for diagnosing your vehicle. Note that all OBD scanners are not the same as some are more advanced than others.


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