On-board diagnostics (OBD) is a term referring to a vehicle's self-diagnostic and reporting capability. 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 on-board vehicle computers. Early versions of OBD would simply illuminate a malfunction indicator light (MIL) or "

idiot light A tell-tale, sometimes called an idiot light or warning light, is an indicator of malfunction or operation of a system, indicated by a binary (on/off) illuminated light, symbol or text legend. The "idiot light" terminology arises from popular f ...

" 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 Real-time data (RTD) is information that is delivered immediately after collection. There is no delay in the timeliness of the information provided. Real-time data is often used for navigation or tracking. Such data is usually processed using real- ...

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.

History

* 1968:

Volkswagen Volkswagen (),English: , . abbreviated as VW (), is a German motor vehicle manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. Founded in 1937 by the German Labour Front under the Nazi Party and revived into a global brand post-W ...

introduces the first on-board computer system, in their

fuel-injected Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All com ...

Type 3 models. This system is entirely analog with no diagnostic capabilities. * 1975: Bosch and Bendix EFI systems are adopted by major automotive manufacturers in an effort to improve tail pipe emissions. These systems are also analog in nature, though some provide rudimentary diagnostic capability through factory tools, such as the Kent Moore J-25400, compatible with the

Datsun 280Z The Nissan S30 (sold in Japan as the Nissan Fairlady Z and in other markets as the Datsun 240Z, then later as the 260Z and 280Z) is the first generation of Z GT 3-door two-seat coupés, produced by Nissan Motors, Ltd. of Japan from 1969 until ...

, and the Cadillac Seville. * 1980: General Motors introduces the first data link on their 1980

Eldorado El Dorado (, ; Spanish for "the golden"), originally ''El Hombre Dorado'' ("The Golden Man") or ''El Rey Dorado'' ("The Golden King"), was the term used by the Spanish in the 16th century to describe a mythical tribal chief (''zipa'') or king o ...

and Seville models. Diagnostic Trouble Codes (DTC's) are displayed through the electronic climate control system's digital readout when in diagnostic mode. * 1981: General Motors introduces its "Computer Command Control" system on all US passenger vehicles for model year 1981. Included in this system is a proprietary 5-pin ALDL interfaces with the

Engine Control Module An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by re ...

(ECM) to initiate a diagnostic request and provide a serial data stream. The protocol communicates at 160 baud with Pulse-width modulation (PWM) signaling and monitors all engine management functions. Real-time sensor data, component overrides, and Diagnostic Trouble Codes. The specification for this link is as defined by GM's Emissions Control System Project Center document XDE-5024B. * 1982:

RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...

defines an analog STE/ICE vehicle diagnostic standard used in the CUCV,

M60 tank The M60 is an American second-generation main battle tank (MBT). It was officially standardized as the Tank, Combat, Full Tracked: 105-mm Gun, M60 in March 1959. Although developed from the M48 Patton, the M60 tank series was never officially ...

and other military vehicles of the era for the US Army. * 1986: General Motors introduces an upgraded version of the ALDL protocol, which communicates at 8192 baud with half-duplex

UART A universal asynchronous receiver-transmitter (UART ) is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. It sends data bits one by one, from the least signific ...

signaling on some models. * 1988: The

California Air Resources Board The California Air Resources Board (CARB or ARB) is the "clean air agency" of the government of California. Established in 1967 when then-governor Ronald Reagan signed the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Moto ...

(CARB) requires that all new vehicles sold in

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

in 1988 and newer vehicles have some basic OBD capability. These requirements are generally referred to as "OBD-I", though this name is not applied until the introduction of OBD-II. The data link connector and its position are not standardized, nor is the data protocol. The Society of Automotive Engineers (SAE) recommends a standardized diagnostic connector and set of diagnostic test signals. * ~1994: Motivated by a desire for a state-wide emissions testing program, the CARB issues the OBD-II specification and mandates that it be adopted for all cars sold in California starting in model year 1996 (see CCR Title 13 Section 1968.1 and 40 CFR Part 86 Section 86.094). The DTCs and connector suggested by the SAE are incorporated into this specification. * 1996: The OBD-II specification is made mandatory for all cars sold in the United States. * 2001: The

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been de ...

makes

EOBD EBD may refer to: * on-board diagnostics, an automotive term referring to a vehicle's self-diagnostic * end of business day, end of day End of day (EOD), end of business (EOB), close of business (COB), close of play (COP) or end of play (EOP) ...

mandatory for all gasoline (petrol) vehicles sold in the European Union, starting in MY2001 (see European emission standards Directive 98/69/EC). * 2004: The

makes

mandatory for all diesel vehicles sold in the European Union * 2006: All vehicles manufactured in Australia and

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

are required to be OBD-II compliant after January 1, 2006. * 2008: All cars sold in the United States are required to use the

ISO 15765-4 ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...

signaling standard (a variant of the

Controller Area Network A Controller Area Network (CAN bus) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other's applications without a host computer. It is a message-based protocol, designed originally for mu ...

(CAN)

bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...

). * 2008: Certain light vehicles in China are required by the Environmental Protection Administration Office to implement OBD (standard GB18352) by July 1, 2008. Some regional exemptions may apply. * 2010: HDOBD (heavy duty) specification is made mandatory for selected commercial (non-passenger car) engines sold in the United States.

Standard interfaces

ALDL

GM's ALDL (Assembly Line Diagnostic Link) is sometimes referred as a predecessor to, or a manufacturer's proprietary version of, an OBD-I diagnostic. 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.

OBD-I

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

, 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 ''on-board'' 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 A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...

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 for OBD-II equipped vehicles.

OBD-1.5

OBD 1.5 refers to a partial implementation of OBD-II which General Motors used on some vehicles in 1994, 1995, & 1996. (GM did not use the term OBD 1.5 in the documentation for these vehicles — they simply have an OBD and an OBD-II section in the service manual.) For example, the 94–95 Corvettes have one post-catalyst oxygen sensor (although they have two

catalytic converter A catalytic converter is an vehicle emissions control, exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalysis, catalyzing a redox chemic ...

s), and have a subset of the OBD-II codes implemented. This hybrid system was present on GM B-body cars (the Chevrolet Caprice, Impala, and Buick Roadmaster) in 94–95,

H-body The H Platform, or H-body, name has been used twice by General Motors. The 1970s H-body was an inexpensive rear-wheel drive compact automobile platform from the 1970s, used for the Chevrolet Vega and Monza and their Buick, Oldsmobile, and Pontia ...

cars in 94–95, W-body cars (Buick Regal, Chevrolet Lumina ('95 only), Chevrolet Monte Carlo ('95 only), Pontiac Grand Prix, Oldsmobile Cutlass Supreme) in 94–95, L-body (Chevrolet Beretta/Corsica) in 94–95, Y-body (Chevrolet Corvette) in 94–95, on the F-body (Chevrolet Camaro and Pontiac Firebird) in 95 and on the J-Body (Chevrolet Cavalier and Pontiac Sunfire) and

N-Body In physics and astronomy, an ''N''-body simulation is a simulation of a dynamical system of particles, usually under the influence of physical forces, such as gravity (see ''n''-body problem for other applications). ''N''-body simulations ar ...

(Buick Skylark, Oldsmobile Achieva, Pontiac Grand Am) in 95 and 96 and also on '94-'95 Saab vehicles with the naturally aspirated 2.3. The pinout for the ALDL connection on these cars is as follows: For ALDL connections, pin 9 is the data stream, pins 4 and 5 are ground, and pin 16 is battery voltage. An OBD 1.5 compatible scan tool is required to read codes generated by OBD 1.5. Additional vehicle-specific diagnostic and control circuits are also available on this connector. For instance, on the Corvette there are interfaces for the Class 2 serial data stream from the PCM, the CCM diagnostic terminal, the radio data stream, the airbag system, the selective ride control system, the low tire pressure warning system, and the passive keyless entry system. An OBD 1.5 has also been used in the Ford Scorpio since 95.

OBD-II

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.

OBD-II diagnostic connector

The OBD-II specification provides for a standardized hardware interface — the female 16-pin (2x8) J1962 connector, where type A is used for 12 Volt vehicles and type B for 24 Volt vehicles. Unlike the OBD-I connector, which was sometimes found under the hood of the vehicle, the OBD-II connector is required to be within of the steering wheel (unless an exemption is applied for by the manufacturer, in which case it is still somewhere within reach of the driver). SAE J1962 defines the pinout of the connector as: The assignment of unspecified pins is left to the vehicle manufacturer's discretion.

EOBD

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 (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic c ...

(

gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organi ...

) engined cars and since January 1, 2004 for

diesel Diesel may refer to: * Diesel engine, an internal combustion engine where ignition is caused by compression * Diesel fuel, a liquid fuel used in diesel engines * Diesel locomotive, a railway locomotive in which the prime mover is a diesel engin ...

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.

EOBD fault codes

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.

EOBD2

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

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

ADR 79/01 & 79/02 (Australian OBD standard)

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

(

) engined cars and since January 1, 2007 for

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 signal protocols

There are five signaling protocols that are permitted with the OBD-II interface. Most vehicles implement only one of the protocols. It is often possible to deduce the protocol used based on which pins are present on the J1962 connector: * SAE J1850 PWM ( pulse-width modulation — 41.6 kB/sec, standard of the

Ford Motor Company Ford Motor Company (commonly known as Ford) is an American multinational automobile manufacturer headquartered in Dearborn, Michigan, United States. It was founded by Henry Ford and incorporated on June 16, 1903. The company sells automobi ...

) **pin 2: Bus+ **pin 10: Bus– **High voltage is +5 V **Message length is restricted to 12 bytes, including CRC **Employs a multi-master arbitration scheme called '

Carrier Sense Multiple Access Carrier-sense multiple access (CSMA) is a medium access control (MAC) protocol in which a node verifies the absence of other traffic before transmitting on a shared transmission medium, such as an electrical bus or a band of the electromagnetic ...

with Non-Destructive Arbitration' (CSMA/NDA) * SAE J1850 VPW ( variable pulse width — 10.4/41.6 kB/sec, standard of General Motors) **pin 2: Bus+ **Bus idles low **High voltage is +7 V **Decision point is +3.5 V **Message length is restricted to 12 bytes, including CRC **Employs CSMA/NDA * ISO 9141-2. This protocol has an asynchronous serial data rate of 10.4 kbit/s. It is somewhat similar to

RS-232 In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' (''data terminal equipment'') such ...

; however, the signal levels are different, and communications happen on a single, bidirectional line without additional handshake signals. ISO 9141-2 is primarily used in Chrysler, European, and Asian vehicles. **pin 7: K-line **pin 15: L-line (optional) **UART signaling **K-line idles high, with a 510 ohm resistor to V_batt **The active/dominant state is driven low with an open-collector driver. **Message length is Max 260Bytes. Data field MAX 255. * ISO 14230 KWP2000 (

Keyword Protocol 2000 Keyword Protocol 2000, abbreviated KWP2000, is a communications protocol used for on-board vehicle diagnostics systems (OBD). This protocol covers the application layer in the OSI model of computer networking. The protocol is standardized by Inter ...

) **pin 7: K-line **pin 15: L-line (optional) **Physical layer identical to ISO 9141-2 **Data rate 1.2 to 10.4 kBaud **Message may contain up to 255 bytes in the data field * ISO 15765 CAN (250 kbit/s or 500 kbit/s). The CAN protocol was developed by Bosch for automotive and industrial control. Unlike other OBD protocols, variants are widely used outside of the automotive industry. While it did not meet the OBD-II requirements for U.S. vehicles prior to 2003, as of 2008 all vehicles sold in the US are required to implement CAN as one of their signaling protocols. **pin 6: CAN High **pin 14: CAN Low All OBD-II pinouts use the same connector, but different pins are used with the exception of pin 4 (battery ground) and pin 16 (battery positive).

OBD-II diagnostic data available

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 parameters that are available 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 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 ...

. 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 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 ...

. Individual manufacturers often enhance the OBD-II code set with additional proprietary DTCs.

Mode of operation/OBD services

Here is a basic introduction to the OBD

communication protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...

according to ISO 15031. In SAE J1979 these "modes" were renamed to "services", starting in 2003. * Service / Mode $01 is used to identify what powertrain information is available to the scan tool. * Service / Mode $02 displays Freeze Frame data. * Service / Mode $03 lists the emission-related "confirmed" diagnostic trouble codes stored. It displays exact numeric, 4 digit codes identifying the faults. * Service / Mode $04 is used to clear emission-related diagnostic information. This includes clearing the stored pending/confirmed DTCs and Freeze Frame data. * Service / Mode $05 displays the oxygen sensor monitor screen and the test results gathered about the oxygen sensor. There are ten numbers available for diagnostics: ** $01 Rich-to-Lean O2 sensor threshold voltage ** $02 Lean-to-Rich O2 sensor threshold voltage ** $03 Low sensor voltage threshold for switch time measurement ** $04 High sensor voltage threshold for switch time measurement ** $05 Rich-to-Lean switch time in ms ** $06 Lean-to Rich switch time in ms ** $07 Minimum voltage for test ** $08 Maximum voltage for test ** $09 Time between voltage transitions in ms * Service / Mode $06 is a Request for On-Board Monitoring Test Results for Continuously and Non-Continuously Monitored System. There are typically a minimum value, a maximum value, and a current value for each non-continuous monitor. * Service / Mode $07 is a Request for emission-related diagnostic trouble codes detected during current or last completed driving cycle. It enables the external test equipment to obtain "pending" diagnostic trouble codes detected during current or last completed driving cycle for emission-related components/systems. This is used by service technicians after a vehicle repair, and after clearing diagnostic information to see test results after a single driving cycle to determine if the repair has fixed the problem. * Service / Mode $08 could enable the off-board test device to control the operation of an on-board system, test, or component. * Service / Mode $09 is used to retrieve vehicle information. Among others, the following information is available: ** VIN (

Vehicle Identification Number A vehicle identification number (VIN) (also called a chassis number or frame number) is a unique code, including a serial number, used by the automotive industry to identify individual motor vehicles, towed vehicles, motorcycles, scooters ...

): Vehicle ID ** CALID (Calibration Identification): ID for the software installed on the ECU ** CVN (Calibration Verification Number): Number used to verify the integrity of the vehicle software. The manufacturer is responsible for determining the method of calculating CVN(s), e.g. using checksum. ** In-use performance counters *** Gasoline engine : Catalyst, Primary oxygen sensor, Evaporating system, EGR system, VVT system, Secondary air system, and Secondary oxygen sensor *** Diesel engine : NMHC catalyst, NOx reduction catalyst, NOx absorber Particulate matter filter, Exhaust gas sensor, EGR system, VVT system, Boost pressure control, Fuel system. * Service / Mode $0A lists emission-related "permanent" diagnostic trouble codes stored. As per CARB, any diagnostic trouble codes that is commanding MIL on and stored into non-volatile memory shall be logged as a permanent fault code. See

for an extensive list of this information.

Applications

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 An original equipment manufacturer (OEM) is generally perceived as a company that produces non-aftermarket parts and equipment that may be marketed by another manufacturer. It is a common industry term recognized and used by many professional or ...

dealership tools to vehicle telematic devices.

Hand-held scan tools

A range of rugged hand-held scan tools is available. * Simple fault code readers/reset tools are mostly aimed at the consumer level. * Professional hand-held scan tools may possess more advanced functions ** Access more advanced diagnostics ** Set manufacturer- or vehicle-specific ECU parameters ** Access and control other control units, such as air bag or ABS ** Real-time monitoring or graphing of engine parameters to facilitate diagnosis or tuning

Mobile device-based tools and analysis

Mobile device applications allow mobile devices such as cell phones and tablets to display and manipulate the OBD-II data accessed via

USB Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad ...

adaptor cables or

Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...

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 of time.

OBD2 Software

An OBD2 software package when installed in a computer (

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ser ...

, Mac, or

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, w ...

) 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

Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wav ...

) plugged in the OBD2 port to enable the vehicle to connect with the computer where the software is installed.

PC-based scan tools and analysis platforms

A PC-based OBD analysis tool that converts the OBD-II signals to serial data (USB or serial port) standard to PCs or Macs. The software then decodes the received data to a visual display. Many popular interfaces are based on the

ELM327 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 ...

or STN OBD Interpreter ICs, both of which read all five generic OBD-II protocols. Some adapters now use the J2534 API allowing them to access OBD-II Protocols for both cars and trucks. In addition to the functions of a hand-held scan tool, the PC-based tools generally offer: * Large storage capacity for data logging and other functions * Higher resolution screen than handheld tools * The ability to use multiple software programs adding flexibility * The identification and clearance of fault code * Data shown by intuitive graphs and charts The extent that a PC tool may access manufacturer or vehicle-specific ECU diagnostics varies between software products as it does between hand-held scanners.

Data loggers

Data loggers are designed to capture vehicle data while the vehicle is in normal operation, for later analysis. Data logging uses include: * Engine and vehicle monitoring under normal operation, for the purposes of diagnosis or tuning. * Some US auto insurance companies offer reduced premiums if OBD-II vehicle data loggers or cameras are installed - and if the driver's behaviour meets requirements. This is a form of auto insurance risk selection * Monitoring of driver behaviour by fleet vehicle operators. Analysis of vehicle

black box In science, computing, and engineering, a black box is a system which can be viewed in terms of its inputs and outputs (or transfer characteristics), without any knowledge of its internal workings. Its implementation is "opaque" (black). The te ...

data may be performed on a periodic basis, automatically transmitted wirelessly to a third party or retrieved for forensic analysis after an event such as an accident, traffic infringement or mechanical fault.

Emission testing

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

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 An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,0 ...

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 computer A trip computer is a computer fitted to some cars; most modern trip computers record, calculate, and display the distance travelled, the average speed, the average fuel consumption, and real-time fuel consumption. The first, mechanical trip co ...

carputer A carputer, or car-puter, is a computer with specializations to run in a car, such as compact size, low power requirement, and some customized components. The computing hardware is typically based on standard PCs or mobile devices. They normally ha ...

or interfaces to PDAs, smartphones, or a

Garmin Garmin Ltd. (shortened to Garmin, stylized as GARMIN, and formerly known as ProNav) is an American, Swiss-domiciled multinational technology company founded in 1989 by Gary Burrell and Min Kao in Lenexa, Kansas, United States, with headquarte ...

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.

Vehicle telematics

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

OBD-II diagnostic trouble codes ( DTCs) contain 1 letter and 4 numbers, and are divided into the following categories: * B – Body (includes air conditioning and airbag) (1164 codes) * C – Chassis (includes ABS) (486 codes) * P – Powertrain (engine and transmission) (1688 codes) * U – Network (wiring bus) (299 codes)

Standards documents

SAE standards documents on OBD-II

*J1962 – Defines the physical connector used for the OBD-II interface. *J1850 – Defines a serial data protocol. There are 2 variants: 10.4 kbit/s (single wire, VPW) and 41.6 kbit/s (2 wire, PWM). Mainly used by US manufacturers, also known as PCI (Chrysler, 10.4K), Class 2 (GM, 10.4K), and SCP (Ford, 41.6K) *J1978 – Defines minimal operating standards for OBD-II scan tools *J1979 – Defines standards for diagnostic test modes *J2012 – Defines standards trouble codes and definitions. *J2178-1 – Defines standards for network message header formats and physical address assignments *J2178-2 – Gives data parameter definitions *J2178-3 – Defines standards for network message frame IDs for single byte headers *J2178-4 – Defines standards for network messages with three byte headers* *J2284-3 – Defines 500K CAN physical and

data link layer The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer ...

*J2411 – Describes the

GMLAN General Motors Local Area Network (GMLAN) is an application- and transport-layer protocol using Controller Area Network for lower layer services. It was standardized as SAE J2411 for use in OBD-II vehicle networks. Transport-layer services Transpo ...

(Single-Wire CAN) protocol, used in newer GM vehicles. Often accessible on the OBD connector as PIN 1 on newer GM vehicles.

SAE standards documents on HD (Heavy Duty) OBD

J1939 Society of Automotive Engineers standard SAE J1939 is the vehicle bus recommended practice used for communication and diagnostics among vehicle components. Originating in the car and heavy-duty truck industry in the United States, it is now widely ...

– Defines a data protocol for heavy duty commercial vehicles

ISO standards

*ISO 9141: Road vehicles – Diagnostic systems.

International Organization for Standardization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Art ...

, 1989. **Part 1: Requirements for interchange of digital information **Part 2: CARB requirements for interchange of digital information **Part 3: Verification of the communication between vehicle and OBD II scan tool *ISO 11898: Road vehicles – Controller area network (CAN). International Organization for Standardization, 2003. **Part 1: Data link layer and physical signalling **Part 2: High-speed medium access unit **Part 3: Low-speed, fault-tolerant, medium-dependent interface **Part 4: Time-triggered communication *ISO 14230: Road vehicles – Diagnostic systems – Keyword Protocol 2000, International Organization for Standardization, 1999. **Part 1: Physical layer **Part 2: Data link layer **Part 3: Application layer **Part 4: Requirements for emission-related systems *ISO 15031: Communication between vehicle and external equipment for emissions-related diagnostics, International Organization for Standardization, 2010. **Part 1: General information and use case definition **Part 2: Guidance on terms, definitions, abbreviations and acronyms **Part 3: Diagnostic connector and related electrical circuits, specification and use **Part 4: External test equipment **Part 5: Emissions-related diagnostic services **Part 6: Diagnostic trouble code definitions **Part 7: Data link security *ISO 15765: Road vehicles – Diagnostics on Controller Area Networks (CAN). International Organization for Standardization, 2004. **Part 1: General information **Part 2: Network layer services

ISO 15765-2 ISO 15765-2, or ''ISO-TP (Transport Layer)'', is an international standard for sending data packets over a CAN-Bus. The protocol allows for the transport of messages that exceed the eight byte maximum payload of CAN frames. ISO-TP segments long ...

**Part 3: Implementation of unified diagnostic services ( UDS on CAN) **Part 4: Requirements for emissions-related systems

Security issues

Researchers at the

University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattl ...

and

University of California The University of California (UC) is a public land-grant research university system in the U.S. state of California. The system is composed of the campuses at Berkeley, Davis, Irvine, Los Angeles, Merced, Riverside, San Diego, San Franci ...

examined the security around OBD, and found that they were able to gain control over many vehicle components via the interface. Furthermore, they were able to upload new firmware into the engine control units. Their conclusion is that vehicle

embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' ...

s are not designed with security in mind. 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

for purposes other than those for which it was designed, and the lack of

authentication Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an assertion, such as the identity of a computer system user. In contrast with identification, the act of indicatin ...

and

authorization Authorization or authorisation (see spelling differences) is the function of specifying access rights/privileges to resources, which is related to general information security and computer security, and to access control in particular. More fo ...

in the OBD specifications, which instead rely largely on

security through obscurity Security through obscurity (or security by obscurity) is the reliance in security engineering on design or implementation secrecy as the main method of providing security to a system or component. History An early opponent of security through o ...

References

;Notes * Birnbaum, Ralph and Truglia, Jerry. ''Getting to Know OBD II''. New York, 2000. . * SAE International. ''On-Board Diagnostics for Light and Medium Duty Vehicles Standards Manual''. Pennsylvania, 2003. .

External links

Directive 98/69/EC of the European Parliament and of the Council of 13 October 1998.

National OBD Clearing House
Center for Automotive Science and Technology at Weber State University
United States Environmental Protection Agency
OBD information for repair technicians, vehicle owners, and manufacturers {{DEFAULTSORT:On-Board Diagnostics Automotive technologies Industrial computing Vehicle security systems