OBD-II is a system in cars that monitors vehicle components, detects faults, and stores information for later retrieval. It was mandated in 1996 and is an improvement on OBD-I, allowing for more sophisticated diagnostic capabilities and the ability to read trouble codes, real-time data, and freeze frame data.
OBD-II is a system used in automobiles to monitor various vehicle components, detect faults, and store the information in the vehicle’s on-board computer for later retrieval by a service technician. OBD-II is an acronym for On Board Diagnostics; the “II” denotes the second and most current version of this technology. Beginning in the early 1970s, vehicles sold in the United States have been equipped with electronic devices to monitor various systems and diagnose malfunctions with the goal of minimizing pollution. This occurred in response to Congress passing the Clean Air Act and establishing the Environmental Protection Agency (EPA) in 1970. These electronic components varied between manufacturers and model years, making retrieval of diagnostic information potentially expensive. and slow.
In 1988, the EPA and the California Air Resources Board (CARB) mandated that vehicle manufacturers include self-diagnostic programs to ensure their emissions equipment would remain effective for the life of the vehicle. The Society of Automotive Engineers standardized a connector and set of diagnostic test signals. Upon equipment failure, this system illuminated a malfunction indicator light (MIL) on the vehicle’s dash, often called the “check engine” light. This system, required on all 1991 and newer cars, became known as On-Board Diagnostics I, or OBD-I.
CARB studies soon concluded that OBD-I systems would not detect emissions components unless they failed completely, and that in some cases the vehicle could still pass an emissions test. The new laws and requirements went into effect on January 1, 1996, the standard adopted for OBD-II. All vehicles built for sale in the US on or after that date are OBD-II equipped.
OBD-II uses various sensors throughout the car to provide the computer, also called the electronic control module (ECM), with information such as engine and ambient temperatures, vehicle speed, etc. The ECM then advances or retards the ignition timing and adds or subtracts fuel accordingly. It also tests the signals from all connected sensors. When a signal is missing or out of specification, the OBD-II system illuminates the MIL and stores its corresponding diagnostic trouble code in its memory.
The OBD-II memory information is read through a connector inside the car. OBD-II improves on OBD-I not only in its more sophisticated diagnostic capabilities, but also because it allows three types of data to be read: trouble codes, real-time data – the raw information from the sensor reported to the OBD-I computer. II and Freeze Frame Data: A “snapshot” of the sensor data at the time the car’s MIL came on. OBD-II codes are read using cables and software created to communicate with OBD-II systems. These can take the form of standalone drives or software that is installed on a PC. Some are complex models intended for professional technicians; The simpler units are priced for hobbyists.
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