Editing On-board diagnostics (section)

==Standard interfaces==

===ALDL===

{{Main|ALDL}}

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.<ref>{{Citation |title=ALDL Bluetooth AdapterUser's Guide |publisher=1320 Electronics LLC }}</ref><ref>{{Cite web|url=http://www.techedge.com.au/vehicle/aldl160/160serial.htm|title = Reading GM's 160 baud ALDL Data Stream with a Standard PC Serial Port}}</ref>

===OBD-I===

The regulatory intent of OBD-I was to encourage auto manufacturers to design reliable [[emission control system]]s that remain effective for the vehicle's "useful life".<ref>{{citation |url=https://www.moreycorp.com/obd-i-obd-ii-a-history-of-on-board-diagnostics/ |title=OBD-I to OBD-II: A History of On-Board Diagnostics |date=December 21, 2022 |publisher=The Morey Corporation |location=US |access-date=2023-03-23}}</ref> The hope was that by forcing annual emissions testing for [[California]] starting in 1988, <ref>{{cite web |url=https://ww2.arb.ca.gov/our-work/programs/obd |title=OBD - On-Board Diagnostic Program |publisher=[[California Air Resources Board]] |location=US |access-date=2024-06-02}}</ref> 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.<ref>{{cite web |url=https://ww2.arb.ca.gov/resources/fact-sheets/board-diagnostic-ii-obd-ii-systems-fact-sheet |title=On-Board Diagnostic II (OBD II) Systems Fact Sheet |publisher=[[California Air Resources Board]] |location=US |date=2019-09-19 |access-date=2024-06-02}}</ref>

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 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 [[Light-emitting diode|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-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 had an OBD and an OBD-II section in the service manual).

For example, the 1994–1995 model year Corvettes have one post-catalyst [[oxygen sensor]] (although they have two [[catalytic converter]]s), and have a subset of the OBD-II codes implemented.<ref>{{cite book | title=1994 Corvette Service Manual, Book 2 | publisher = General Motors Corporation |date=December 1993 | pages = 6E3–A-166 : 6E3–A-223}}</ref>

This hybrid system was present on GM [[General Motors B platform|B-body]] cars (the Chevrolet Caprice, Impala, and Buick Roadmaster) for 1994–1995 model years, [[General Motors H platform (1986)|H-body]] cars for 1994–1995, [[General Motors W platform|W-body]] cars (Buick Regal, Chevrolet Lumina) for 1995 only, Chevrolet Monte Carlo (1995 only), Pontiac Grand Prix, Oldsmobile Cutlass Supreme (for 1994–1995), [[General Motors L platform|L-body]] (Chevrolet Beretta/Corsica) for 1994–1995, [[General Motors Y platform|Y-body]] (Chevrolet Corvette) for 1994–1995, on the [[General Motors F platform|F-body]] (Chevrolet Camaro and Pontiac Firebird) for 1995 and on the [[General Motors J platform|J-Body]] (Chevrolet Cavalier and Pontiac Sunfire) and [[General Motors N platform|N-Body]] (Buick Skylark, Oldsmobile Achieva, Pontiac Grand Am) for 1995 and 1996 and also for North American delivered 1994–1995 [[Saab Automobile|Saab]] vehicles with the naturally aspirated 2.3.

The pinout for the ALDL connection on these cars is as follows:
{| class="wikitable" style="text-align:center"
| 1 || 2 || 3 || 4 || 5 || 6 || 7 || 8
|-
| 9 || 10 || 11 || 12 || 13 || 14 || 15 ||16
|}

For ALDL connections, pin 9 is the data stream, pins 4 and 5 are ground, and pin 16 is the 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.<ref>{{cite book | title=1994 Corvette Service Manual, Book 2 | publisher = General Motors Corporation | date = Dec 1993 | pages = 6E3–A–11}}</ref>

An OBD 1.5 has also been used in the [[Ford Scorpio]] since 95.<ref>{{cite web |url=http://www.fordscorpio.co.uk/star.htm |title=EEC IV Code Reader: For 2.9L 12 Valve & Early Tdi |website=Ford Scorpio |location=UK |date=2006-01-14 |access-date=2024-06-02}}</ref>

===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 (automotive)|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====
[[Image:OBD 002.jpg|thumb|right|270px|Female OBD-II connector on a car]]
[[Image:OBD-II type A female connector pinout.svg|thumb|right|Female OBD-II type A connector pinout – front view]]
[[Image:OBD-II type B female connector pinout.svg|thumb|right|Female OBD-II type B connector pinout – front view. Wire placement is identical to type A, but the center groove is split in two.]]

The OBD-II specification provides for a standardized hardware interface — the female 16-pin (2x8) [[Data link connector (automotive)#OBD-II diagnostic connector|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 bonnet of the vehicle, the OBD-II connector is required to be within {{convert|2|ft|m}} 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:

{| class="wikitable"
|- valign="top"
!  1
| '''Manufacturer discretion'''<br>
GM: J2411 GMLAN/SWC/Single-Wire CAN.<br>
Audi: Switched +12 to tell a scan tool whether the ignition is on.<br>
VW: Switched +12 to tell a scan tool whether the ignition is on.<br>
Mercedes<ref>{{cite web |url=https://pinoutguide.com/CarElectronics/mercedes_obd2_diag_pinout.shtml |title=Mercedes PinOut |website=Pinoutguide.com |date=2019-09-30 |access-date=2022-12-27}}</ref> (K-Line): Ignition control (EZS), air-conditioner (KLA), PTS, safety systems (Airbag, SRS, AB) and some other.
!  9
| '''Manufacturer discretion'''<br>
GM: 8192 baud ALDL where fitted.<br>
BMW: RPM signal.<br>
Toyota: RPM signal.<br>
Mercedes (K-Line): ABS, ASR, ESP, ETS, BAS diagnostic.
|- valign="top"
! style="background-color: blue" |  2
| '''[[Bus (computing)|Bus]] positive Line'''<br>
[[SAE J1850]] PWM and VPW
! style="background-color: blue" | 10
| '''Bus negative Line'''<br>
SAE J1850 PWM only (not SAE 1850 VPW)
|- valign="top"
! 3
| '''Manufacturer discretion'''<br>
Ethernet TX+ (Diagnostics over IP)<br>
Ford DCL(+) Argentina, Brazil (pre OBD-II) 1997–2000, USA, Europe, etc.<br>
Chrysler CCD Bus(+)<br>
Mercedes (TNA): TD engine rotation speed.
! 11
| '''Manufacturer discretion'''<br>
Ethernet TX- (Diagnostics over IP)<br>
Ford DCL(-) Argentina, Brazil (pre OBD-II) 1997–2000, USA, Europe, etc.<br>
Chrysler CCD Bus(-)<br>
Mercedes (K-Line):&nbsp;Gearbox and other transmission components (EGS, ETC, FTC).
|- valign="top"
! style="background-color: gray" |  4
| '''Chassis ground'''
! 12
| '''Manufacturer discretion'''<br>
Ethernet RX+ (Diagnostics over IP)<br>
Mercedes (K-Line):&nbsp;All activity module (AAM), Radio (RD), ICS (and more)
|- valign="top"
! style="background-color: gray" |  5
| '''Signal ground'''
! 13
| '''Manufacturer discretion'''<br>
Ethernet RX- (Diagnostics over IP)<br>
Ford: FEPS – Programming PCM voltage<br>
Mercedes (K-Line):&nbsp;AB diagnostic – safety systems.
|- valign="top"
! style="background-color: lime" |  6
| '''CAN high'''<br>
(ISO 15765-4 and SAE J2284)
! style="background-color: lime" | 14
| '''CAN low'''<br>
(ISO 15765-4 and SAE J2284)
|- valign="top"
! style="background-color: yellow" |  7
| '''K-line'''<br>
(ISO 9141-2 and ISO 14230-4)
! style="background-color: yellow" | 15
| '''L-line'''<br>
(ISO 9141-2 and ISO 14230-4)
|- valign="top"
!  8
| '''Manufacturer discretion'''<br>
Activate Ethernet (Diagnostics over IP)<br>
Many BMWs: A second K-line for non OBD-II (Body/Chassis/Infotainment) systems.<br>
Mercedes: Ignition<br>
! style="background-color: red" | 16
| '''Battery voltage'''<br>
(+12 Volt for type A connector)<br>
(+24 Volt for type B connector)
|}

The assignment of unspecified pins is left to the vehicle manufacturer's discretion.<ref>{{cite web |url=https://pinoutguide.com/CarElectronics/car_obd2_pinout.shtml |title=OBD II diagnostic interface pinout |website=Pinoutguide.com |date=2017-12-02 |access-date=2022-06-28}}</ref>

===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 {{cvt|2500|kg|lb|disp=comma}} or less) first registered within EU member states since January 1, 2001 for [[petrol]]-engined cars and since January 1, 2004 for [[Diesel fuel|diesel]] engined cars.<ref>{{cite web |url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31998L0069:EN:HTML |title=Directive 98/69/EC of the European Parliament |publisher=Publications Office of the European Parliament}}</ref>

For newly introduced models, the regulation dates applied a year earlier – January 1, 2000 for petrol and January 1, 2003, for diesel.<br />
For passenger cars with a Gross Vehicle Weight rating of greater than 2500&nbsp;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.<ref>{{Cite web |title=Blog {{!}} Indramat USA |url=https://indramat-usa.com/blog/rexroth-fault-codes |access-date=2023-10-27 |website=indramat-usa.com}}</ref> 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.<ref>{{Cite web|url=http://www.obd-codes.com/trouble_codes/|title=OBD-II Check Engine Light Trouble Codes}}</ref>

===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 ('''A'''ustralian '''D'''esign '''R'''ule '''79/01''' – Emission Control for Light Vehicles, 2005) is the Australian equivalent of OBD-II. It applies to all vehicles of category M1 and N1 with a Gross Vehicle Weight rating of {{cvt|3500|kg|lb}} or less, registered from new within Australia and produced since January 1, 2006 for [[petrol]]-engined cars and since January 1, 2007 for [[Diesel fuel|diesel]]-engined cars.<ref>{{cite web |url=http://www.comlaw.gov.au/Details/F2008C00323|title=Vehicle Standard (Australian Design Rule 79/01 – Emission Control for Light Vehicles) 2005|date=April 28, 2007 |publisher=Australian Government ComLaw}}</ref>

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&nbsp;kg or less, from July 1, 2008, for new models, July 1, 2010, for all models.<ref>{{cite web |url=http://www.comlaw.gov.au/Details/F2010C00476|title=Vehicle Standard (Australian Design Rule 79/02 – Emission Control for Light Vehicles) 2005|date=June 30, 2010 |publisher=Australian Government ComLaw}}</ref>

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/EMD+ ===

In North America, EMD and EMD+ are on-board diagnostic systems that were used on vehicles with a gross vehicle weight rating of {{cvt|14,000|lb|kg}} or more between the 2007 and 2012 model years if those vehicles did not already implement OBD-II. EMD was used on California emissions vehicles between model years 2007 and 2009 that did not already have OBD-II. 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. EMD+ was used on model year 2010-2012 California and Federal petrol-engined vehicles with a gross vehicle weight rating of over {{cvt|14,000|lb|kg}}, it added the ability to monitor nitrogen oxide catalyst performance. EMD and EMD+ are similar to OBD-I in logic but use the same SAE J1962 data connector and CAN bus as OBD-II systems.<ref name="Ford manual" />