Modern cars contain many sensors, actuators and computers. These help produce, read, and process data about the car's current state, including faults and general operating parameters.

An OBD port facilitates a secondary computer to be plugged into the cars onboard ECU, allowing the data to be downloaded and even displayed in real-time. For mechanics and drivers, an OBD port is a time saver and key to keeping your car healthy. 

The physical OBD port is a standardised connection between all car makes and models. But the software can be less universal. Today, we're discussing everything you need to know about these ports, so forget Googling "What is an OBD port?" Instead, scroll down to find out what an OBD port is used for and other frequently asked questions. 

What is an OBD port? 

An OBD port is a universal connector port that mechanics can use to run tests and diagnostics on your car’s computer. The port only refers to the outlet space where the mechanic can plug the OBD equipment (a computer and long cable). 

This is done to know the status of the car’s sub-systems, and it can even help you detect faults or maintenance problems before they arise. But more about these details below. 

What does OBD port stand for? 

On-Board Diagnostics. 

What is an OBD port used for?  

Now you know what an OBD port is, let’s dive into what it’s used for.  

Like most connections between computers, data can be transferred in both directions in an OBD port. This allows more than just the reading of stored error codes. Here are some ways an OBD port is used:  

Reading data  

There are ten different sensors and data streams on a modern car, including basic things such as engine temperature and RPM. But for an ECU to do its job, it needs to know everything about the vehicle, from exhaust gas composition to throttle pedal position.   

These parameters are available to a mechanic or vehicle owner with the proper diagnostic tools. For example, even a basic OBD reader can tell exactly what temperature the engine coolant is at or the engine timing.  

Diagnosing problems can be made much easier by using the data to eliminate possibilities, such as ruling out a faulty throttle pedal sensor - a common issue on some cars - by examining the percentages outputted to the ECU through an OBD tool.  

Reading stored codes  

When a fault develops, the ECU can detect the abnormality via the sensors above. In most cases, something like a misfire caused by faulty spark plugs will simply cause the engine warning light to illuminate.  

After the problem has occurred, even if it is an intermittent fault - the ECU will store the relevant information in its memory. This is then displayed as a code when viewed, allowing a mechanic to diagnose the problem.  

Modifying your car  

Because the ECU defines the car and engine so much, many parameters can be modified to suit the driver or upgrade the vehicle.  

With the relevant software, changes can be made, such as increasing the engine’s performance - also known as a remap - and tweaking the way the lights operate to be more convenient.  

There are some consumer-grade options for doing this, such as Carly.

Will an OBD scanner tell me what’s wrong with my car? 

Yes, an OBD scanner will tell you what’s wrong with your car. But it’s not always that simple. 

OBD reading provides fault codes that identify when certain tests have failed. You only extract information, which needs to be interpreted to understand if there’s anything wrong with your car.  

The codes can’t pinpoint exact faults or tell you what needs to be repaired. However, a mechanic or a knowledgeable driver can use the codes to understand what the tests have indicated.  

If you’re unsure about OBD codes, it’s best to work with a professional mechanic to learn more. 

Why is an OBD port required? 

An OBD port is required to monitor your car to keep it functional and secure. They’re here to make diagnostic checks easier, allowing you to fix any problems before they harm you or other drivers. 

What is the difference between OBD1 and OBD2?  

The beauty of the OBD system is that the ports are standardised, allowing any car to be connected using the same cable in a similar way that USB is the standard for mobile phones and laptops.   

However, the car technology was pretty limited because the first iteration of OBD (OBD1) was introduced in 1981. This meant certain features we now take for granted had not been made commonplace. 

It was only added to certain cars sold in specific locations, mostly from American manufacturers to the Californian market.   

OBD2 was introduced in 1996 and included many more features. This new standard was developed to be future-proof, unlike OBD1, and is still used today. 

What year cars have OBD2?  

OBD2 was introduced in 1996, but not all manufacturers adopted it immediately. Many makers only introduced it due to legislation. The list below will help identify whether your car has an OBD. 

• Cars made for the US market - All cars from 1996 
• Petrol cars made for the EU market - All cars from 2000 
• Diesel cars made for the EU market - All cars from 2004

Remember, your car may have an OBD2 plug, even if made before these dates. Check below for where to find your OBD port to be certain.  

Where is my OBD2 port?  

Whilst all manufacturers differ on the best place to put the port, there are some usual places to check first, namely under the dashboard. The port will rarely be in the engine bay. Some cars hide the port using a piece of plastic trim. It may have 'OBD' written on it.  

The best way to check your specific car is to read the user manual. Failing that, a quick search online will almost always help. Don't forget to include the year of your car.  

Can you clear codes with an OBD2 scanner? 

Yes. An OBD2 scanner allows you to check diagnostic codes and clear internal codes when not needed.  

How do I test my OBD port?  

If you have tried to plug in a device to your OBD port, and it’s not working correctly, it may be difficult to pinpoint the cause.   

First, check the OBD connector for damaged pins or breaks to the cable. If you have access to another OBD scan tool or device, try that. Alternatively, if you have another car with an OBD port, try connecting your device to that.   

If these tests prove fruitless, they may require a garage trip. Their professional equipment will be able to tell why the port is not responding as it should and advise on how best to fix it.

How do I clear OBD codes? 

You can clear OBD codes by: 

• Find your OBD Port & connect the OBD scanner 
• Turn on the car’s ignition 
• Select “Read Codes” on the scanner 
• Press “Clear/Erase” codes 
• Disconnect scanner when completed 

Remember, OBD error codes should only be cleared when the vehicle has been repaired or is deemed road-safe. You might also want to write down the codes for future reference. 

Can you drive with an OBD tool plugged in?  

Yes! There are a few devices that are designed to be used this way. Also, gauges and control devices, for example, allow you to read extra information about your car while moving.   

It is best to only use devices that enable wireless communication, such as those with Bluetooth that connect to a smartphone, to avoid cables running in the driver's footwell.   

Ensure you have a passenger to monitor these devices, though you should not use any mobile device while controlling a vehicle.  

Can you clear OBD codes while driving? 

Yes. You can drive with an OBD tool plugged in and you can clear some OBD codes while driving. However, this isn’t advised as you should have your complete attention on the road. Consider clearing codes with the engine running but the car in a stationary position instead. 

What OBD scanner should I buy?  

If you need to read some error messages stored in your ECU, want to know more about your engine, or are just curious, there is a wide range of products to choose from to suit every budget.   

Basic tools  

For around £20, you can buy a basic scanner tool. These typically plug in via a cable and display basic error messages and system parameters such as engine temp, RPM, throttle position, ignition timing, and more.  

They can't typically change any parameters, though, and are difficult to use to gather data whilst on the move.   

Advanced Scanners  

If you're willing to drop a bit more cash, for around £50-£100, you can get tools that will do all of the above.    

Devices like Carly can change your car's lighting and mirrors, allowing auto-dipping mirrors when reversing. They can also display ECU error messages.  

As well as displaying the error messages, these levels of tools often have built-in libraries of information that can help diagnose problems. Sometimes, they even guide you through step-by-step troubleshooting using physical and digital tests on the car.   

Many connect to your phone or laptop via Bluetooth, meaning you can easily use them whilst on the move to get more information.  

Professional Scanners  

Aimed at garages and mechanics, these tools often run into the hundreds of pounds and offer connection to manufacturer-specific software, such as those used by BMW and VW, to enable further customization.   

Due to the complexity of these systems, they are often used in conjunction with a laptop computer and sometimes need a certain amount of training to operate effectively.   

For more information on OBD tools, Tom’s Guide did a tremendous run-down here.  

What is the best OBD2 scanner for beginners? 

If you’re new to OBD scanners, you might want to opt for a basic scanner first. Buying an affordable basic scanner tool will help you learn more about your car’s OBD port, and from there, you can decide whether you want to buy a more complex tool or work with mechanics instead. 

Will any OBD2 scanner work on my car? 

No. Though OBD2 is a universal standard, there is a chance that the scanner isn’t compatible with your vehicle. Always check whether your chosen scanner is suitable for your car before purchasing.  

What is an OBD port - The bottom line 

OBD ports are essential in emergencies and when you want to check your car’s health. Knowing what type of OBD port you have and where it is can help you access this information faster, so check your car out now to save time and money in the future.  

We hope this information has clued you in on all things OBD ports. Bookmark this blog to keep the information handy! 

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Author - Joseph Law

Joseph has been writing about cars for over seven years and writing for Bumper for over two, blending his passion for automobiles with a talent for storytelling.

Joseph has written about engineering and cars for Autozilla, Komaspec, and several engineering manufacturers. When he's not writing or tinkering with one of his five cars, Joseph dreams of owning an Alfa Romeo 33 Stradale.