What are the OBD2 Protocols?
OBD2 scanners put out information using a specialized “language,” also referred to as an “OBD2 protocol “.
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Modern vehicles make use of an onboard diagnostic system (or OBD2) that can help both vehicle owners and specialists diagnose difficult-to-identify problems using diagnostic trouble codes (or DTCs). If you have ever noticed the “check engine” light on your dashboard (also known as the “MIL” or malfunction indicator light), then you know that your OBD2 system has noticed an error during regular operation.
In the past, the MIL simply indicated a problem was present, without any further details. Today, home mechanics and specialists alike have access to OBD2 scanners that provide actionable information straight from your vehicle’s main computer without needing to take the care apart.
OBD2 scanners put out information using a specialized “language,” also referred to as an “OBD2 protocol.” Different makes and models may use different protocols, depending on their manufacture year and location. Historically, there have been several different OBD2 protocols, differentiating how vehicles interface with scanners.
Different types of OBD2 Protocols
Current OBD2 standards permit five different protocol types – ISO 14230-4 KWP2000. SAE J1850 VPW, SAE J1850 PWM, ISO 15765-4 CAN, and ISO 9141-2. Though the 16-pin plug-in port on most modern vehicles appears visually the same, their 16-pin arrangement and function differ protocol to protocol. Most modern scanners can read any protocol type, but it is still important to know your vehicle’s specific protocol.
Which OBD2 protocol is supported by my vehicle?
Each vehicle, regardless of manufacturer, supports at least one type of OBD2 protocol. In fact, some vehicles now (especially those manufactured in the US) feature more than one type of OBD2 protocol (a result of federal standards). Knowing which protocol your vehicle supports may help you troubleshoot current and future vehicle problems.
The table below includes a list of the five current OBD2 protocol types, as well as which manufacturers or countries use them.
OBD2 Protocol Type Common Manufacturer or Country/Region
SAE J1850 VPW General Motors
SAE J1850 PWM Ford Motor Company
ISO 9141-2 Chrysler; European, Asian
ISO 14230-4 KWP2000 Asian (Rare)
ISO 15765-4 CAN United States (all vehicles since 2008)
How to check the OBD2 protocol on your vehicle
When checking what OBD2 protocols your vehicle supports, be sure to take note of the manufacturer and model year. Both can determine the precise protocol or protocols used. The chart above provides a general overview of the types of OBD2 protocols used by each manufacturer and manufacturing region. However, there is a simple visual check that can be performed if you want to determine the precise protocols supported by your vehicle.
Identifying The Location Of Your OBD2 Connector Port
First, you’ll need to identify the location of your OBD2 connector port (see below for more detailed instructions). This is usually located under the dashboard (though it may be covered or obscured by paneling). Next, procure a light source and shine it directly upon the port, enough to create a reflection off of the shiny metal pin ends.
Inspect The Pin Ends
Next, inspect the pin ends. Do this by numbering the pins 1-16 left to right, top to bottom (as seen in the diagram below). As you do this, take note of which ends do and do not contain metallic ends. Most OBD2 protocols use a unique pin arrangement, so you will be able to differentiate your vehicle’s precise protocol using this method.
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Once you’ve taken note of which pins contain a metallic end, consult the table below in order to determine precisely which protocol your vehicle communicates using. Some imported vehicles use entirely unique or proprietary OBD2 protocols, so be sure to consult your owner’s manual for further details.
OBD2 Protocol Type and Metallic Pin End Arrangement
OBD2 Protocol Type Metallic Pin End Arrangement
SAE J1850 PWM 2, 4, 5, 10, and 16
SAE J1850 VPW 2, 4, 5, and 16 (not 10)
ISO 9141-2/ ISO 14230-4 KWP2000 4, 5, 7, 15, and 16
ISO 15765-4 CAN 4, 5, 6, 14 and 16
Where is the Connector Located?
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Every vehicle manufactured since 1996 (when the OBD2 standards were implanted in the US) include an easily-assessable OBD2 connector port. Your vehicle will feature the same 16-pin connector port regardless of its manufacturer. Locating it is an easy but crucial step towards testing your vehicles OBD2 output, as well as freeze frame data.
On most modern vehicles, the OBD2 connector port is located beneath the dashboard. This may also include the left and right of the steering column. The port may be obscured by a piece of removable paneling, so be sure to check carefully and thoroughly. Otherwise, check-in or around the glove compartment on the passenger side. For further location information, consult your owner’s manual.
No matter what model vehicle you own, current standards dictate that the OBD2 connector port cannot be further than three feet from the driver and cannot be covered by any plate that requires tools to remove.
Finding the right OBD2 scan tool for your vehicle
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Home mechanics and specialists alike today have access to OBD2 scan tools. You can even pick one up at most auto parts stores. Because the OBD2 standards are widely adopted, you will likely be able to use an OBD2 scan tool on your vehicle. As long as the scan tool was manufactured since 1996, it should be compatible with your vehicle’s OBD2 connector port.
What you need to know when you perform your OBD2 test
OBD2 tests are one of the best ways for you to acquire legible data regarding your vehicle’s performance. OBD2 output this information in a variety of methods, including freeze frame data and diagnostic trouble codes (DTC). While these codes can be interpreted using manufacturer-specific listings online, you may need to consult with a specialist in order to act upon this information.
OBD2 tests generally output “unseen” information regarding your car’s performance when an error occurred, including coolant temperature and engine load. In order to acquire some of this information, you may need to input a PID (Parameter ID) into your testing device to acquire a specific piece of information.
Conclusion
OBD2 protocols differ from vehicle to vehicle, but they uniformly act as the language through which your vehicle outputs information regarding its own performance. Now that you’ve learned about the different OBD2 protocol types, as well as how to identify your vehicle’s specific protocol type, you’ll be able to run OBD2 tests with ease. As a result, you’ll be better prepared to diagnose any vehicle problem that arises with ease.
