Hands down, OBD2 is the new global standard in On Board Diagnostics and most vehicles manufactured since MY 1996 up to present were already using the OBD2 standard with a 16pin OBD2 port. So we will no longer discuss topics in relation to OBD1 port or the DLCs-Diagnostic Link Connectors used in OBD1.
If you purchased a car after 1996, chances are it has an OBD2 port. Every car or truck on the road manufactured after 1996 is legally mandated to have one installed. It’s a 16pin female connector or socket installed in your car located near the dash, above the pedal or anywhere near the steering column as a standard requirement.
OBD2 is an on-board computer that monitors emissions, mileage, speed, and other data about your car. It’s connected to the Check Engine light, which illuminates when the computer detects a problem.
The OBD2 on-board computer features a 16-pin port located under the driver’s side dash. It allows a mechanic or anyone else to read the error code using a special scan tool.
There are five basic signal protocols:
SAE J1850 PWM: Pulse Width Modulation used in Ford vehicles
SAE J1850 VPW: Variable Pulse Width used in General Motors vehicles
ISO9141-2: Used in all Chrysler and a variety of European or Asian vehicles
ISO14230-4 (KWP2000): Keyword Protocol, used in a variety of European and Asian imports as well as Honda, Jeep, Land Rover, Subaru, Mazda, Nissan, and more
ISO 15765 CAN: Controller Area Network, used on all vehicles manufactured after 2008
Pins 4 and 5 in all protocols are used for ground connections, and pin 16 is used for power from the car’s battery.
Once the computer senses a problem with the engine or any other component of the car it’s monitoring, it’ll trigger the Check Engine light. Some vehicles also blink the engine light if the problem is a very serious one.
How Does OBD2 Work?
Diagnostic Trouble Codes (DTC) are stored in the computer system. Codes can vary from one manufacturer to another. However, anyone with an OBD2 scan tool can connect to the port and read the diagnostic trouble codes from the computer.
The reason any OBD2 scan tool can read the codes is because of the standardized pinout. Scan tools can read from any of the protocols listed above. The standardized pinout is as follows.
Pin 1: Used by manufacturer
Pin 2: Used by SAE J1850 PWM and VPW
Pin 3: Used by manufacturer
Pin 4: Ground
Pin 5: Ground
Pin 6: Used by ISO 15765-4 CAN
Pin 7: The K-Line of ISO 9141-2 and ISO 14230-4
Pin 10: Used only by SAE J1850 PWM
Pin 14: Used by ISO 15765-4 CAN
Pin 15: The K-Line of ISO 9141-2 and ISO 14230-4
Pin 16: Power from the car battery
OBD2 scanners can connect to these ports and identify the trouble code from any manufacturer that uses one of the OBD2 protocols.
What Can Be Hooked Up to the OBD-2 Port?
Traditionally, a mechanic would hook up a scan tool to the port to read the DTC. Less expensive scanners would only provide a numeric code, which the mechanic would then look up from the manufacturer’s manual or service website. More expensive scanners provide will provide text error codes.