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OBD-II PIDs (On-board diagnostics Parameter IDs) are codes used to request data from a vehicle, used as a diagnostic tool. SAE standard J1979 defines many OBD-II PIDs. All on-road vehicles and trucks sold in North America are required to support a subset of these codes, primarily for state mandated emissions inspections .
The typical modern TCU uses signals from engine sensors, automatic transmission sensors and from other electronic controllers to determine when and how to shift. [2] More modern designs share inputs or obtain information from an input to the ECU, whereas older designs often have their own dedicated inputs and sensors on the engine components.
OBD-II is an improvement over OBD-I in both capability and standardization. The OBD-II standard specifies the type of diagnostic connector and its pinout, the electrical signalling protocols available, and the messaging format. It also provides a candidate list of vehicle parameters to monitor along with how to encode the data for each.
The ELM327 is a programmed microcontroller produced for translating the on-board diagnostics (OBD) interface found in most modern cars. The ELM327 command protocol is one of the most popular PC-to-OBD interface standards and is also implemented by other vendors.
The description of Mode 3 DTC parameter data seems to be specific to CAN-bus OBD-II ECUs. Older, pre-2003 OBD-II ECUs (i.e., J1850 VPW/PWM, ISO 9142-2 and Keyword 2000) pack DTC data into multiple OBD-II response packets somewhat differently. --Bruce D. Lightner 17:00, 14 December 2011 (UTC)
The data link connector (DLC) is the multi-pin diagnostic connection port for automobiles, trucks, and motorcycles used to interface a scan tool with the control modules of a given vehicle and access on-board diagnostics and live data streams.
The service "ECU reset" is used to restart the control unit (ECU). Depending on the control unit hardware and implementation, different forms of reset can be used: 0x11 01 Hard Reset simulates a shutdown of the power supply. 0x11 02 key Off-On Reset simulates the drain and turn on the ignition with the key.
When the MIL is lit, the engine control unit stores a fault code related to the malfunction, which can be retrieved—although in many models this requires the use of a scan tool. This warning light can indicate almost anything from a loose gas cap to a serious knock or fault in the engine. [4]