What is OBD? Standards, Pin arrangement of connector terminals

　・In Japanese

■What is OBD?

OBD (On Board Diagnostics) is a component failure diagnosis performed inside the car. If a part that affects exhaust gas is malfunctioning, the MIL (Malfunction Indicator Lamp) will light up on the meter, and if a component that does not affect exhaust gas is malfunctioning, a master warning will be displayed. In a narrow sense, OBD refers to the failure diagnosis of parts that affect exhaust gas.

If the light comes on, the user must go to the car dealer for repair. The dealer uses a scan tool to extract various information flowing on CAN communication from the OBD connector under the driver's seat. and determine the cause of the failure.

＜History of OBD＞
OBD became popular in California in the 1980s. Due to its topography, California has poor air circulation, which makes it easy for exhaust gases to accumulate. And California has many liberal people and is highly aware of the global environment, so California has the world's highest exhaust gas regulations.

At that time, OBD support was still different among manufacturers, and failure diagnosis codes and OBD connector shapes were not standardized. Later on, with OBD-II, the DLC (Data Link Connector) shape and failure codes were unified. It has become a standard (SAE J1979).

In the future, it will be called OBDonUDS, and it will become a standard (SAE J1979-2) that standardizes the OBD protocol and UDS (Unified Diagnostic Services) protocol,which used to coexist. Information on whether OBD diagnosis is being performed properly (IUMPR: In-Use Monitor Performance Ratio) and more detailed information at the time of failure (FFD: Freeze Frame Data) can now be extracted using a common standard.

■DLC pin arrangement

■DTC code

DTC (Diagnostic Trouble Code) is a four-digit code assigned to each type of failure. Each ECU stores this code when a part fails, so when you extract the information with GST(Generic Scan Tool), you can find out which part has failed. Code numbers are defined by ISO15031, SAE J2012, etc. as follows.

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