What Is OBD, OBD2?What is the difference between these two?


You may be surprised at the many things that are hidden under your vehicle’s dashboard. That is where almost every onboard system of the car is located. It basically is the entry point to everything that makes the whole vehicle tick.

If you are curious enough you’ve probably inspected the driver’s compartment. Just under the dashboard, above the brake pedal is a 16-pin port popularly known as the OBD port. In some vehicles, it’s found below the gearbox, in others beside the steering wheel and others have it at the foot of the passenger seat.

Either way, with a proper car diagnostic tool, you can access all the vehicle’s systems through that port. That process can either be OBD, OBD2 or EOBD. On this page, you will learn all about those three, including EOBD2.

What is OBD?

OBD is short for “On-Board Diagnostics”. It is a standardized system that allows a vehicle’s computer to interface with external electronic devices. The devices are popularly known as OBD scanners or OBD scan tools.

By doing so, OBD gives the vehicle the ability to do self-diagnosis and reporting. In short, when you connect a car diagnostic toolwith the onboard computer you will have access to several vehicle subsystems. Consequently, you can check their statuses and even repair those that are faulty using the information provided on the car diagnostic tool.

OBD was originally developed to primarily reduce emissions by monitoring the performance of an engine’s main components. Additionally, it was meant to diagnose the electronic fuel injection system that was adopted by automakers on a large scale in the early 1980s.

In its most basic form, the OBD system is made up of an Electronic Control Unit (ECU), sensors and actuators. The ECU collects input from sensors (like oxygen sensors, mass air flow sensors, and voltage sensors) and then uses it to control actuators (like fuel injectors and hydraulic cylinders) to get the desired performance.

Usually, the car itself will warn you in advance when there’s a malfunction. It does so using the Check Engine Light, otherwise known as the Malfunction Indicator Light (MIL). Now when the light comes on, you use a car diagnostic tool to access the ECU and check sensors and actuators for faults.

There are two types of OBD, namely OBD1 and OBD2.


OBD1 is the first generation of OBD systems. Developed in the 1980s, they were made by automakers for their own cars. Meaning there was an OBD1 scanner for each brand of cars.

While a car owner could buy one car diagnostic tool that is designed for his/her vehicle a mechanic needed to buy at least one tool for every vehicle make. You can imagine the number of scanners a mechanic needed to have at any given time!

Generally, the OBD1 system features protocols, hardware interfaces and proprietary connectors. Nowadays there are OBD1 car diagnostic tools that support multiple protocols. You only need to buy adapter cables for all the different vehicle makes that you want to run diagnostics on.

Although OBD1 was used all through 1995, the push to standardize the system only came in 1991 after the California Air Resources Board (CARB) made it mandatory that all vehicles sold in the state have OBD capabilities.

Despite the effort, it was still lacking in functionality. That prompted the introduction of the OBD2 system – the second generation of OBD. More on the shortcomings of OBD1 in a short while but for now let’s look at OBD2.


OBD2 was first introduced in vehicles made in 1994. It became a mandatory requirement for all cars and light trucks made from 1996 onward. In case you are wondering, it’s still the system being used today in all vehicles sold domestically.

This system basically features a set of standards that describe how a car diagnostic tool and ECU interchange digital information. All OBD2-compliant vehicles have a universal connector (the SAE J1962) and use one standard OBD2 communication protocol.

That’s all technical information, but what you need to know is that all vehicles sold in the US since 1996 use the OBD2 standard. As such, they come with an OBD2 port – usually located just below the dashboard – where an OBD2 car diagnostic tool plugs. Once the connection is established you will have access to the vehicle’s onboard computers.

Difference between OBD1 and OBD2

While both systems are similar in primary functionality, they vary widely in many other ways. But how exactly are they similar? To put it simply, they both check sensors and actuators for such things as shorts, opens and high resistance.

In terms of differences, the first is when each one was implemented. While the OBD1 gained wide usage in 1991, OBD2 became a universal standard in 1996. The 5-year difference also saw several improvements in functionality.

For starters, the original OBD only targeted emission control of a vehicle. Even so, it was not really effective in getting motorists to move their emission handle system tests. On the other hand, OBD2 has enhanced signaling protocols that read a wide array of emission parameters at a go.

With regards to diagnostics, OBD2 does a better job of checking the engine and its performance. It inspects regions of fault, pinpoints problems and in some cases even helps in correcting them. Additionally, OBD2 checks for engine efficiency, that’s why it’s largely synonymous with the Check Engine Light.

The same cannot be said about OBD1. Even with the most advanced car diagnostic tool, you can only read trouble codes. OBD1 doesn’t pinpoint faults and neither does it perform the same engine efficiency tests as OBD2.

In fact, whereas the instructions for OBD2 are given as alphanumeric codes the original OBD1 only had CEL and SES instructions. And they couldn’t access as many onboard vehicle systems as OBD2 do.

When it comes to standardization, OBD1 failed to gain success because most manufacturers had their own versions. The differences in standards made it necessary to introduce OBD2. The latter is a standardized system that is used by all vehicles manufactured after 1996.

Overall, OBD2 is a better program that runs standardized tests and offers universal trouble codes and repair options. For mechanics that means using virtually the same procedures for all types of OBD2-compliant vehicles. In addition to making the work easier, you can use one car diagnostic tool for several vehicles makes.

OBD1 vs. OBD2 Chart

Here’s a chart summarizing the differences between these two systems:

Introduction 1991 1996
Nature Semi-automatic self-diagnostic system Fully automatic self-diagnostic system
Function Fully automatic self-diagnostic system  Fully automatic self-diagnostic system
Standardization Not standardized Standardized on all vehicles made from 1996
Application Californian standard Federal standard
Interface Manufacturer-specific Universal



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