On-board diagnostics
The amount of diagnostic information available via OBD has varied widely since its introduction in the early 1980s versions of onboard vehicle computers.
Modern OBD implementations use a standardized digital communications port to provide real-time data and diagnostic trouble codes which allow malfunctions within the vehicle to be rapidly identified.
This interface was made in different varieties and changed with power train control modules (aka PCM, ECM, ECU).
[15][16] The regulatory intent of OBD-I was to encourage auto manufacturers to design reliable emission control systems that remain effective for the vehicle's "useful life".
Technical difficulties with obtaining standardized and reliable emissions information from all vehicles led to an inability to implement the annual testing program effectively.
[19] The Diagnostic Trouble Codes (DTC's) of OBD-I vehicles can usually be found without an expensive scan tool.
By connecting certain pins of the diagnostic connector, the 'Check Engine' light will blink out a two-digit number that corresponds to a specific error condition.
Cadillac fuel-injected vehicles are equipped with actual onboard diagnostics, providing trouble codes, actuator tests and sensor data through the new digital Electronic Climate Control display.
For example, the 1994–1995 model year Corvettes have one post-catalyst oxygen sensor (although they have two catalytic converters), and have a subset of the OBD-II codes implemented.
The OBD-II standard specifies the type of diagnostic connector and its pinout, the electrical signalling protocols available, and the messaging format.
OBD-II Diagnostic Trouble Codes are 4-digit, preceded by a letter: P for powertrain (engine and transmission), B for body, C for chassis, and U for network.
Mercedes[23] (K-Line): Ignition control (EZS), air-conditioner (KLA), PTS, safety systems (Airbag, SRS, AB) and some other.
Ethernet TX- (Diagnostics over IP) Ford DCL(-) Argentina, Brazil (pre OBD-II) 1997–2000, USA, Europe, etc.
The technical implementation of EOBD is essentially the same as OBD-II, with the same SAE J1962 diagnostic link connector and signal protocols being used.
[27] The term "EOBD2" is marketing speak used by some vehicle manufacturers to refer to manufacturer-specific features that are not actually part of the OBD or EOBD standard.
[29] The technical implementation of this standard is essentially the same as OBD-II, with the same SAE J1962 diagnostic link connector and signal protocols being used.
EMD was required to monitor fuel delivery, exhaust gas recirculation, the diesel particulate filter (on diesel engines), and emissions-related powertrain control module inputs and outputs for circuit continuity, data rationality, and output functionality.
OBD-II provides access to data from the engine control unit (ECU) and offers a valuable source of information when troubleshooting problems inside a vehicle.
Newer devices on the market are equipped with GPS sensors and the ability to transmit vehicle location and diagnostics data over a cellular network.
Modern OBD-II devices can therefore nowadays be used to for example locate vehicles, monitor driving behavior in addition to reading Diagnostics Trouble Codes (DTC).
[36][37] An OBD-II software package when installed in a computer (Windows, Mac, or Linux) can help diagnose the onboard system, read and erase DTCs, turn off MIL, show real-time data, and measure vehicle fuel economy.
Many popular interfaces are based on the ELM327 or STN[41] OBD Interpreter ICs, both of which read all five generic OBD-II protocols.
Instrumentation may take the form of dedicated trip computers,[47] carputer or interfaces to PDAs,[48] smartphones, or a Garmin navigation unit.
OBD II information is commonly used by vehicle telematics devices that perform fleet tracking, monitor fuel efficiency, prevent unsafe driving, as well as for remote diagnostics and by pay-as-you-drive insurance.
It can be used to detect reckless driving in real time based on the sensor data provided through the OBD port.
OBD II is also monitored to block mobile phones when driving and to record trip data for insurance purposes.
[50] OBD-II diagnostic trouble codes (DTCs)[51][52] are five characters long, with the first letter indicating a category, and the remaining four being a hexadecimal number.
[57] The primary causes of this vulnerability lie in the tendency for vehicle manufacturers to extend the bus for purposes other than those for which it was designed, and the lack of authentication and authorization in the OBD specifications, which instead rely largely on security through obscurity.
