Автокөліктердегі диагностика терминологиясы

Automotive engineering terminology

On board diagnostics (OBD) is a term referring to a vehicle's self diagnostic and reporting capability. In the United States, this self diagnostic is a requirement to comply with Federal Emissions standards to detect failures that may increase the vehicle tailpipe emissions to more than 150% of the standard to which it was originally certified. A primary benefit of this is that OBD systems give the vehicle owner or repair technician access to the status of the various vehicle sub systems. The amount of diagnostic information available via OBD has varied widely since its introduction in the early 1980s versions of onboard vehicle computers. Early versions of OBD would simply illuminate a malfunction indicator light (MIL) or "idiot light" if a problem was detected, but would not provide any information as to the nature of the problem. Modern OBD implementations use a standardized digital communications port to provide real time data in addition to a standardized series of diagnostic trouble codes, or DTCs, which allow a person to rapidly identify and remedy malfunctions within the vehicle.

GM's ALDL (Assembly Line Diagnostic Link) is sometimes referred to as a predecessor to, or a manufacturer's proprietary version of, an OBD I diagnostic starting in 1981. This interface was made in different varieties and changed with power train control modules (aka PCM, ECM, ECU). Different versions had slight differences in pin outs and baud rates. Earlier versions used a 160 baud rate, while later versions went up to 8192 baud and used bi directional communications to the PCM.

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". The hope was that by forcing annual emissions testing for California starting in 1988, and denying registration to vehicles that did not pass, drivers would tend to purchase vehicles that would more reliably pass the test. OBD I was largely unsuccessful, as the means of reporting emissions specific diagnostic information was not standardized. Technical difficulties with obtaining standardized and reliable emissions information from all vehicles led to an inability to implement the annual testing program effectively. The Diagnostic Trouble Codes (DTC's) of OBD I vehicles can usually be found without an expensive scan tool. Each manufacturer used their own Diagnostic Link Connector (DLC), DLC location, DTC definitions, and procedure to read the DTC's from the vehicle. DTC's from OBD I cars are often read through the blinking patterns of the 'Check Engine Light' (CEL) or 'Service Engine Soon' (SES) light. 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. The DTC's of some OBD I cars are interpreted in different ways, however. Cadillac (gasoline) 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. Holding down 'Off' and 'Warmer' for several seconds activates the diagnostic mode without the need for an external scan tool. Some Honda engine computers are equipped with LEDs that light up in a specific pattern to indicate the DTC. General Motors, some 1989–1995 Ford vehicles (DCL), and some 1989–1995 Toyota/Lexus vehicles have a live sensor data stream available; however, many other OBD I equipped vehicles do not. OBD I vehicles have fewer DTC's available than OBD II equipped vehicles.

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. There is a pin in the connector that provides power for the scan tool from the vehicle battery, which eliminates the need to connect a scan tool to a power source separately. However, some technicians might still connect the scan tool to an auxiliary power source to protect data in the unusual event that a vehicle experiences a loss of electrical power due to a malfunction. Finally, the OBD II standard provides an extensible list of DTCs. As a result of this standardization, a single device can query the on board computer(s) in any vehicle. This OBD II came in two models OBD IIA and OBD IIB. OBD II standardization was prompted by emissions requirements, and though only emission related codes and data are required to be transmitted through it, most manufacturers have made the OBD II Data Link Connector the only one in the vehicle through which all systems are diagnosed and programmed. 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.

The European on board diagnostics (EOBD) regulations are the European equivalent of OBD II, and apply to all passenger cars of category M1 (with no more than 8 passenger seats and a Gross Vehicle Weight rating of 2500 kg or less) first registered within EU member states since January 1, 2001 for petrol (gasoline) engined cars and since January 1, 2004 for diesel engined cars. For newly introduced models, the regulation dates applied a year earlier – January 1, 2000 for petrol and January 1, 2003, for diesel. For passenger cars with a Gross Vehicle Weight rating of greater than 2500 kg and for light commercial vehicles, the regulation dates applied from January 1, 2002, for petrol models, and January 1, 2007, for diesel models. 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. With Euro V and Euro VI emission standards, EOBD emission thresholds are lower than previous Euro III and IV.

Each of the EOBD fault codes consists of five characters: a letter, followed by four numbers. The letter refers to the system being interrogated e. g. Pxxxx would refer to the powertrain system. The next character would be a 0 if complies to the EOBD standard. So it should look like P0xxx. The next character would refer to the sub system. P00xx – Fuel and Air Metering and Auxiliary Emission Controls. P01xx – Fuel and Air Metering. P02xx – Fuel and Air Metering (Injector Circuit). P03xx – Ignition System or Misfire. P04xx – Auxiliary Emissions Controls. P05xx – Vehicle Speed Controls and Idle Control System. P06xx – Computer Output Circuit. P07xx – Transmission. P08xx – Transmission. The following two characters would refer to the individual fault within each subsystem.

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. In this case "E" stands for Enhanced.

JOBD is a version of OBD II for vehicles sold in Japan.

The ADR 79/01 (Vehicle Standard (Australian Design Rule 79/01 – Emission Control for Light Vehicles) 2005) standard is the Australian equivalent of OBD II. It applies to all vehicles of category M1 and N1 with a Gross Vehicle Weight rating of 3500 kg or less, registered from new within Australia and produced since January 1, 2006 for petrol (gasoline) engined cars and since January 1, 2007 for diesel engined cars. For newly introduced models, the regulation dates applied a year earlier – January 1, 2005 for petrol and January 1, 2006, for diesel. The ADR 79/01 standard was supplemented by the ADR 79/02 standard which imposed tighter emissions restrictions, applicable to all vehicles of class M1 and N1 with a Gross Vehicle Weight rating of 3500 kg or less, from July 1, 2008, for new models, July 1, 2010, for all models. 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.

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. The SAE J1979 standard defines a method for requesting various diagnostic data and a list of standard parameters that might be available from the ECU. The various available parameters are addressed by "parameter identification numbers" or PIDs which are defined in J1979. For a list of basic PIDs, their definitions, and the formula to convert raw OBD II output to meaningful diagnostic units, see OBD II PIDs. Manufacturers are not required to implement all PIDs listed in J1979 and they are allowed to include proprietary PIDs that are not listed. The PID request and data retrieval system gives access to real time performance data as well as flagged DTCs. For a list of generic OBD II DTCs suggested by the SAE, see Table of OBD II Codes. Individual manufacturers often enhance the OBD II code set with additional proprietary DTCs.

Various tools are available that plug into the OBD connector to access OBD functions. These range from simple generic consumer level tools to highly sophisticated OEM dealership tools to vehicle telematic devices.

Mobile device applications allow mobile devices such as cell phones and tablets to display and manipulate the OBD II data accessed via USB adaptor cables or Bluetooth adapters plugged into the car's OBD II connector. 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). Even more advanced devices allow users to reset engine DTC codes, effectively turning off engine lights in the dashboard; however, resetting the codes does not address the underlying issues and can in worst case scenarios even lead to engine breakage where the source issue is serious and left unattended for long periods.

An OBD2 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. To use OBD2 software, one needs to have an OBD2 adapter (commonly using Bluetooth, Wi Fi or USB) plugged in the OBD2 port to enable the vehicle to connect with the computer where the software is installed.

In the United States, many states now use OBD II testing instead of tailpipe testing in OBD II compliant vehicles (1996 and newer). Since OBD II stores trouble codes for emissions equipment, the testing computer can query the vehicle's onboard computer and verify there are no emission related trouble codes and that the vehicle is in compliance with emission standards for the model year it was manufactured. In the Netherlands, 2006 and later vehicles get a yearly EOBD emission check.

Driver's supplementary vehicle instrumentation is instrumentation installed in a vehicle in addition to that provided by the vehicle manufacturer and intended for display to the driver during normal operation. This is opposed to scanners used primarily for active fault diagnosis, tuning, or hidden data logging. Auto enthusiasts have traditionally installed additional gauges such as manifold vacuum, battery current etc. The OBD standard interface has enabled a new generation of enthusiast instrumentation accessing the full range of vehicle data used for diagnostics, and derived data such as instantaneous fuel economy. Instrumentation may take the form of dedicated trip computers, carputer or interfaces to PDAs, smartphones, or a Garmin navigation unit. As a carputer is essentially a PC, the same software could be loaded as for PC based scan tools and vice versa, so the distinction is only in the reason for use of the software. These enthusiast systems may also include some functionality similar to the other scan tools.

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. Although originally not intended for the above purposes, commonly supported OBD II data such as vehicle speed, RPM, and fuel level allow GPS based fleet tracking devices to monitor vehicle idling times, speeding, and over revving. By monitoring OBD II DTCs a company can know immediately if one of its vehicles has an engine problem and by interpreting the code the nature of the problem. It can be used to detect reckless driving in real time based on the sensor data provided through the OBD port. This detection is done by adding a complex events processor (CEP) to the backend and on the client's interface. OBD II is also monitored to block mobile phones when driving and to record trip data for insurance purposes.

OBD II diagnostic trouble codes (DTCs) are five characters long, with the first letter indicating a category, and the remaining four being a hexadecimal number. The first character, representing category can only be one of the following four letters, given here with their associated meanings. (This restriction in number is due to how only two bits of memory are used to indicate the category when DTCs are stored and transmitted). There have been reports of thieves using specialist OBD reprogramming devices to enable them to steal cars without the use of a key. 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.