The OBD2 protocol defines how your vehicle transmits data to your scanner. Read this article to know how to find the protocol you have and how to use it.
Every vehicle made after 1996 must have an On-board Diagnostic Version 2 (OBD2) computer that can self-check the vehicle for issues. For most people. That should be good enough.
Most off-the-shelf OBD2 diagnostic scanners can read any OBD2 compliant system. Because of this, you only need to know which OBD2 protocol you have when you replace your vehicle’s hardware.
However, knowing which protocol you have may come handy. So, here is a quick guide to the five standard OBD2 protocols currently in the market.
What is OBD2 Protocol?
Vehicle self-diagnostic systems existed since the 1969s when Volkswagen introduced them to the world. These onboard computers give vehicle owners and repair technicians crucial information on the current state of the engine and other subsystems. However, they were highly manufacturer-specific unto the 1990s.
In 1991, California legislators created the first universal OBD standard as a way to reduce vehicle exhaust emissions. The standard was expanded nationwide five years later to become the OBD2 standard the industry currently uses. You are guaranteed to have a compliant vehicle if it was made afterward,
OBD2 Protocol Connectors
The standard mandates that all vehicles monitor and record certain vehicle operating parameters. You access this data through a universal OBD2 diagnostic link connector. This connector comes in two variants as defined by the SAE J196 electronics standard.
Both connector formats are 16-pin, female, D-shape connectors with a groove situated between the two rows of pins. Designed for 12-volt systems, type A has its groove running the full length of the port. On the other hand, type B has a split groove and can withstand voltages up to 24 volts.
Beyond these connector types, the OBD2 standard defines five different manufacturer-specific protocols. Each OBDII protocol defines how the data is collected, but are otherwise completely compatible with each other.
In fact, you can use any compliant scanner with any of the protocols. There will be some translation issues, but nothing to prevent you from doing your job.
Types of OBD2 Protocols
As mentioned before there are five different variations to the OBD2 standard.
Here is the OBD2 protocol list:
- SAE J1850 VPW
- SAE J1850 PWM
- ISO 9141-2
- ISO 14230 KWP2000
- ISO 15765-4/SAE J2480 (CAN)
SAE J1850 VPW
This GM-specific variable pulse width just sets the transmission encoding of the data. It runs are 10.4 kbps along Data Pin 1. With the protocol, high and low signal strengths define the data bits.
SAE J1850 PWM
You typically find this pulse-width modulation protocol in Ford models. It uses a 41.6 kbps signal along Pins 1 and 2 with the data represented as voltage shirts in the signal.
You find this protocol on Chrysler, European, and Asian vehicle made before 2004. It uses a 10.4 kbps signal on pins 7 and 15. This old data format uses asynchronous serial communication.
ISO 14230 KWP2000
The Keyword Protocol 2000 is the enhanced version of the ISO 9141-2 standard which it replaced. It also uses asynchronous serial transmission along pins 7 (the K-line) and 15 (the L line). You see it often on Chrysler, European, and Asian makes and models after 2003.
It does have two sub-protocols, though they only differ in how they initiate data transfers
- Slow or 5-baud – communicates with speeds ranging from 1.2 to 10.4 kbps
- Fast – Only transmits at 10.4 kbps
ISO 15765-4/SAE J2480 (CAN)
ISO 15765 is the true protocol standard of the OBD2 specification. All vehicles sold in the U.S. after 2008 must use it. It uses a two-wire, differential format that can reach speeds up to 1Mbps. The protocol transmits on pins 6 and 14 with pins 4 and 5 set to ground.
The protocol also comes with four sub-specifications:
- ISO 15765-4 CAN (11-bit ID,500 Kbaud)
- ISO 15765-4 CAN (29-bit ID,500 Kbaud)
- ISO 15765-4 CAN (11-bit ID,250 Kbaud)
- ISO 15765-4 CAN (29-bit ID,250 Kbaud)
Note some Fiat, Alfa, and Lancia models to use a fault-tolerant version, but they are not OBD2 compliant.
Which OBD2 Protocol is Supported By My Vehicle? Examine the Pins!
For most scanners, you just need an OBD2-compliant vehicle. You can normally use any scanner with any protocol. However, there are times when you want to be more specific.
Not every OBD2 protocol connects with the scanner the same way. Unfortunately, the only way to know what protocol you have is to look at the pin datasheet of your vehicle’s connector.
Fortunately, you only need to concern yourself with the internal teeth. The various protocols have pin requirements. So, you can tell which you have by seeing which pins are present and which ones are missing. In other words, which pins have metal contacts in the connector housing.
To get you started, here is a list of every pin location in the OBD2 standard:
Top 8 Pins
- Reserved for OEM COMM
- J1850 Bus+ (positive)
- OEM Reserved
- Framework/car chassis ground
- Sensor signal ground
- OEM COMM / CAN High
- OEM Reserved
Bottom 8 Pins
- OEM COMM
- J1850 Bus- (negative)
- OEM Reserved
- OEM Reserved
- OEM Reserved
- OEM Reserved / CAN Low
- Power out (12 volts)
You have to match this layout with the physical pins in your vehicle to see which OBD2 protocol you have.
|OBD2 Protocols||Pin 2||Pin 4||Pin 5||Pin 6||Pin 7||Pin 10||Pin 14||Pin 15||Pin 16|
|SAE J1850 VPW||X||X||X||X|
|SAE J1850 PWM||X||X||X||X||X|
|ISO 14230 KWP2000||X||X||X||X||X|
|ISO 15765-4/SAE J2480 (CAN)||X||X||X||X||X|
The Bottom Line
Since its inception in 1996, the OBD2 standard offered several different data transmission protocols to improve communication between different diagnostic tools.
While mostly interchangeable today, these variants can cause trouble with older equipment.
By assessing your vehicle’s OBD2 protocol, you can elevate any potential issues by ensuring that you use only the right scanners and tools.
We hope this article helps guide you through the process.
If you are still not sure, you can contact our representatives and we will walk you through it so you can get the right tool for the job.