What Is OBD1, OBD2, EOBD and EOBD2?

Today's cars and trucks are literally rolling beds of technology, and the portal to their inner workings is something called an onboard diagnostic system, or OBD for short. All vehicles built within the last two decades have one, and it's accessed via a port that’s usually situated behind a latch or within a small compartment beneath the dashboard on the driver’s side. Sometimes, it resides in a vehicle’s glove box.

When the “check engine” warning illuminates on your car's instrument panel or the vehicle is otherwise suffering mechanical issues, a technician can plug an electronic OBD scanner into the port to determine what’s wrong. You can do it yourself with the proper device if you’re handy.

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 tool with 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.

In this case, OBD-II is used as a general term and can mean any of the following:

  • OBD II (California ARB)
  • EOBD (European OBD)
  • JOBD (Japanese OBD)


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:








Semi-automatic self-diagnostic system

Fully automatic self-diagnostic system


Access ECU and diagnose sensors and actuators

Access ECU and diagnose sensors and actuators


Not standardized

Standardized on all vehicles made from 1996


Californian standard

Federal standard





OBD1 vs OBD2: How to tell


What is EOBD?

One more thing about OBD is that it is an American standard. If you are in Europe then you would be dealing with the EOBD. That’s an abbreviation for European On-Board Diagnostics. It’s basically the European version of OBD2.

This system applies to all gasoline and diesel vehicles sold in Europe since 2001 and 2003 respectively. Every EOBD-compliant vehicle has a standard port like the OBD2 port where a car diagnostic tool plugs in. It too is a universal 16-pin port.

EOBD was introduced following the European Directive 98/69/EC. The primary aim was to monitor and reduce emissions from vehicles. Just as is the case with OBD2, EOBD monitors and stores information collected from sensors and actuators. Whenever a fault is detected, the system relays a diagnostic trouble code (DTC).

Modern EOBD car diagnostic tools not only display DTCs but also interpret the codes, show live sensor data and provide repair recommendations.

Ultimately, the introduction of EOBD leads to the standardization of diagnostic systems. Each vehicle basically features a fault code memory that can be accessed with a car diagnostic tool. With a good tool, you will have unrestricted access to all the emission systems.

Additionally, EOBD provides a platform for retrieving uniform fault codes regardless of the make of the vehicle. Car owners and mechanics use the codes (and other diagnostic data) to do repairs and maintenance.



Contrary to what many people think, EOBD2 is NOT a later or second generation of EOBD. The abbreviation actually stands for Enhanced On-Board Diagnostics, 2nd Generation. And it refers to manufacturer-specific features that automakers add to OBD2 and EOBD tools.

EOBD2 features make it possible to access additional data and parameters that you otherwise wouldn’t have access to with an ordinary OBD2 or EOBD car diagnostic tool. Since they are manufacturer-specific, EOBD2 tools only work on the vehicle brands they are designed for. For example, an EOBD2 tool that is made for Ford cars cannot work on a Toyota.


The Takeaway Points

In sum, OBD1 and OBD2 differ in functionality as well as the time of introduction. As such, an OBD1 vehicle requires completely different protocols and even car diagnostic tools from its OBD2 counterpart. Knowing which type of car you are dealing with will help a great deal.

While OBD1 and OBD2 are different systems, OBD2 and EOBD are similar in virtually every aspect. The only difference is that EOBD is made for vehicles that are sold in Europe. On the other hand, OBD2 is designed for cars and light trucks that are targeted for the American market.

So whether you have an OBD2 or EOBD scanner you will have access to almost the same diagnostic features.