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WHAT IS OBD?
OBD stands for “On-Board Diagnostics.” It is a computer-based system originally designed to reduce emissions by monitoring the performance of major engine components.
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Which OBD-II protocol is supported by my vehicle?
All cars and light trucks built for sale in the United States after 1996 are required to be OBD-II compliant. The European Union OBD legislation is somewhat more complicated.
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What is an OBD adapter?
Communication protocols used in modern vehicles are incompatible with standard computer protocols (RS-232, USB, and so on). An OBD adapter (sometimes referred to as “vehicle interface adapter”) is an electronic device that allows a computer to access the vehicle network. It is similar in operation to a computer modem or a gateway, in that it translates messages from one protocol to another.
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What data is available from OBD?
OBD-II offers a standard way to access many types of data, including:
Real-time parameters: RPM, speed, pedal position, spark advance, airflow rate, coolant temperature, etc.
Status of “Check Engine” light
Emission readiness status
Freeze frame: a “snapshot” of parameters at the time a trouble event has occurred.
Diagnostic trouble codes (DTCs).
Oxygen sensor test results
Vehicle Identification Number (VIN)
Number of ignition cycles
Number of miles driven with MIL on넶42 2021-01-27
What is an OBD adapter?
Communication protocols used in modern vehicles are incompatible with standard computer protocols (RS-232, USB, and so on). An OBD adapter (sometimes referred to as “vehicle interface adapter”) is an electronic device that allows a computer to access the vehicle network. It is similar in operation to a computer modem or a gateway, in that it translates messages from one protocol to another.
Normally, the data flows both ways — to and from the ECU. For example, in order to display the RPM or trouble codes, the following series of events must take place:
1、Software sends a request for RPM to the OBD adapter via one of the standard channels (e.g., USB).
2、OBD adapter receives the request, and retransmits it to the ECU on one of the OBD protocols (e.g., J1850).
3、The ECU responds with the data, the OBD adapter relays the reply back to the software.
4、The software decodes the reply, and displays it to the user.
