Automotive Diagnostic Systems - From OBD to Open Diagnostics Exchange format

Advanced automotive diagnostic systems

From OBD to Open Diagnostics Exchange format (ODX) and limits and potentials of
standardization processes

Before getting to ODX, itself, we need a quick review of OBD. Electronic ignitions and fuel
injection systems were the first major steps in getting away from mechanical fuel delivery and
ignition. Being able to control the volume of fuel and sparking it at the right time are critical
in controlling emissions, as well as making the vehicle more fuel efficient. Miniaturization and
developments in computer technology enabled a closer control over that efficiency, and, along
with it, the monitoring of contaminants.

All the while the technology was unfolding it was realized that not only that it was beneficial
but that it needed standardization. The diagnostic codes needed to be read in a manner
better than specialized machines. A brief word is needed about standardization processes.
They do not often occur in a convivial environment, as there are many competing commercial
interests. Many times, a corporation will invest millions of dollars in developing a product,
hoping that others will follow suit. There is a catch, however, if people can become dependent
upon the way that product acts, then, the developers stand potentially to gain enormously
from patent rights. A classic case of dependency was with the fiber optic FC (“ferrule
connector”). During the early 1990s, there were many fights in the Electronic Industries
Association and Institute for Electrical and Electronics Engineers standards committees among
fiber optic cable developers about which standard was to prevail. It would be more convenient
for everyone to follow, but more important, if everyone had to use company X's product
because it was the standard, then that dependency would be established. The same is true for
automotive diagnostic equipment being standardized. Major corporations will send
representatives to these standardization committees to thrash out the issues and present
their arguments. While not the usual decorum, physical fights have been known to break out
at these standardization meetings.

In 1988 the Society of Automotive Engineers argued for a uniform diagnostic connector and
standardized test signals. After it became apparent that the original OBD was not going to be
very useful for universal use or for governments to incorporate into air quality legislation

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pertaining to automobiles, it was realized that further work was needed. Hence, came the
OBD-II development.

Yet, there still exist many problems in standardization. For example, automobile
manufacturers use five basic OBD-II protocols:

• J1850 PWM
• J1850 VPW
• ISO9141
• ISO14230 (also known as Keyword Protocol 2000)
• CAN (ISO15765/SAEJ2480)

[9]

Chrysler, as well as every European manufacturer and the majority of the Asian
manufacturers use ISO 9141 circuitry. GM uses SAE variable pulse width modulation (VPM)
patterns, while Ford uses SAE J1850 pulse width modulation (PWM) patterns. These three
communicate with the standard 16-pin, J1962 connector, but there are different protocols.
One can differentiate between the pin usage by inspection. Systems using the ISO 9141
protocol locate a pin in position number 7 and a pin in either position number 2 or 10
position. SAE protocol-based systems do not have pins with connections in position number 7.
There are systems called 'OBD-II' that are compliant with laws and goes by the name of
“European OBD (EOBD). There also is the Japanese variety, called ‘JOBD’ [10].

Specifically standard to the OBD-II are:

• Type of connectors and number of pins – 16
• Signaling protocols that can be used – limited to the five
• Format of messages
• A list of what is to be monitored
• Methods for data coding
• Power pin that can connect to the car battery
• List of diagnostic trouble codes (DTC).
[11]

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Based on all this ODX was able to be created. As indicated by its name, “Open Diagnostics
Exchange format”, or ODX, the industry was moving towards a uniform way of OBD. The
Association for Standardization of Automation and Measuring Systems [12] is responsible for
the ODX. ASAM was initiated by German car manufacturers and, in its own words, “...provides
standards for data models, interfaces and syntax specifications for a variety of applications,
such as testing, evaluation and simulation.” Actually, ODX is a “market name”, the actual
name being “Data Model for ECU [electronic control unit] Diagnostics (also: Open Diagnostic
Data Exchange Format) V2.2.0 18 May 2008 [13].” Since 1998, numerous automobile
manufacturers from all around the world have joined, and jointly, they create standards for
International Organization for Standards (ISO) approval [14]. The ODX, created in 2002,
went numerous revisions, and is stable enough for use. There were 25 core members, 19
companies, and three countries that formed the standard [A report by the ODX ISO project
leader, A. Schleicher is available on-line [15]. As specified by the ISO website:

The ODX specification contains the data model to describe all diagnostic data of a vehicle and
physical ECU, e.g. diagnostic trouble codes, data parameters, identification data, input/output
parameters, ECU configuration (variant coding) data and communication parameters. ODX is
described in Unified Modelling Language (UML) diagrams and the data exchange format uses
Extensible Mark-up Language (XML).

The ODX modelled diagnostic data describe:
• protocol specification for diagnostic communication of ECUs;
• communication parameters for different protocols and data link layers and for ECU
software;
• ECU programming data (Flash);
• related vehicle interface description (connectors and pinout);
• functional description of diagnostic capabilities of a network of ECUs;
• ECU configuration data (variant coding).

The purpose of ISO 22901-1:2008 is to ensure that diagnostic data from any vehicle
manufacturer is independent of the testing hardware and protocol software supplied by any
test equipment manufacturer.
[16]

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Diagnostic tools and equipment

While computerized automotive diagnosis was reserved initially for dealerships, not much
time had elapsed until after market devices started appearing in auto parts stores. One can
buy hand held devices that plug into the wiring harness of a car and determine what is wrong
by reading diagnostic codes. However, these are not as complete as those devices available
to dealership service technicians. At the dealerships, however, the devices are more
complicated and give readouts that correspond to specifications described in automotive
service manuals. Components other than the power train are diagnosed, such as airbags and
brakes. Cars can be diagnosed while running, and some of the equipment includes display
screens that give graphical representations of what is happening.

The OBD-II standard requires a 16 pin female connector in the car that has the following
configuration:
1. Manufacturer discretion. GM: J2411 9. -
GMLAN/SWC/Single-Wire CAN.

2. Bus positive Line of SAE-J1850 PWM 10. Bus negative Line of SAE-J1850 PWM
and SAE-1850 VPW only (not SAE-1850 VPW)

3. Ford DCL(+) Argentina, Brazil (pre 11. Ford DCL(-) Argentina, Brazil (pre
OBD-II) 1997-2000, USA, Europe, etc. OBD-II) 1997-2000, USA, Europe, etc.
Chrysler CCD Bus(+) Chrysler CCD Bus(-)

4. Chassis ground 12. -

5. Signal ground 13. -

6. CAN high (ISO 15765-4 and SAE- 14. CAN low (ISO 15765-4 and SAE-
J2284) J2284)

7. K line of ISO 9141-2 and ISO 14230- 15. L line of ISO 9141-2 and ISO 14230-
4 4

8. - 16. Battery voltage
[17]
The nonstandard part is the allowance of the manufacturer to assign unspecified pins.
The next logical step in complexity is an actual computer – desktop or laptop. These
computers can accommodate any diagnostic setup with any of the OBD-II protocols. As can

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be expected, there is a greater depth of computation and analysis, along with higher screen
resolution, and storage capacity to contain data on individual vehicles either for future
retrieval or cross-vehicle analysis. Software varies, of course, but if one can imagine that
something should be done with respect to OBD, in all probability, the application exists. From
this level of computerization of OBD there emerged the XML-based data description format,
the extensible markup language format, based on the hypertext markup language (HTML
code used for web page development. With this format anyone, especially vehicle
manufactures and their suppliers, can store and keep current data of the vehicle life cycle,
including design, manufacturer, and maintenance data, in a standardized way.

Both with hand-held and computer-based automotive diagnosis, those responsible for
monitoring and enforcing vehicle emissions and safety standards can keep better track of
various systems. So often in the past, the old methods of visual inspection and subjectivity in
reading gauges and meters cannot keep pace with a technology demanding precise tolerances
in measurements. Just a two percent variance on a sensor can mean the difference between
whether the car operates within an acceptable limit or not. Not only for the automotive
diagnostician but for the motorist various OBD-type devices are installed to warn the car
owner of impending difficulties, with the idea that prevention of a problem is much simpler
than repair. Sensor warning lights that give notice about problems concerning air bags,
brakes or engine (such as “Check Engine” on the Chevrolet Cavalier) are a part of the chain of
technology enabling accurate automotive diagnosis.

Over the years, the value of flight data recorders has been realized. Knowing what brought
down an airliner proves valuable in designing safer planes and improving how they are flown.
The same applies to automobiles, and some insurance companies are giving discounts for the
installation of a data recorder in automobiles. By monitoring the driver's behavior, it is
thought that the safer drivers would pay a lower premium. The same system is being
instituted for fleet drivers, as well [18].

Want to learn more about current technologies
and developments in advanced automotive diagnostic systems?
Visit our Download Centre for more articles, whitepapers and interviews:
http://bit.ly/automotive-diagnostics

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References

[1] VAD - http://acronyms.thefreedictionary.com/Vehicle+Automated+Diagnostic+System
[2] http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=930966
[3] http://en.wikipedia.org/wiki/On-board_diagnostics#cite_note-3 - 1994 Corvette Service
Manual, Book 2. General Motors Corporation. December 1993. pp. 6E3–A-166: 6E3–A-223.
[4] http://en.wikipedia.org/wiki/On-board_diagnostics#EOBD
[5] CCR Title 13 Section 1968.1 and 40 CFR Part 86 Section 86.094
[6] European emission standards Directive 98/69/EC - http://eur-
lex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:1998L0069:19981228:EN:PDF
[7] http://en.wikipedia.org/wiki/On-board_diagnostics#cite_note-2
[8] http://en.wikipedia.org/wiki/On-board_diagnostics
[9] http://www.obd-codes.com/faq/obd-ii-protocols.php
[10] http://www.cvel.clemson.edu/auto/systems/OBD.html
[12] ASAM - http://www.asam.net/home/
[13] http://www.asam.net/home/standards/?no_cache=1&pointer=3
[14]
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=41207

[15] https://docs.google.com/viewer?url=http://www.testing-
expo.com/europe/07txeu_conf/pres/day_2/day_2_3.pdf&embedded=true&chrome=true.
[16]
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=41207
[18] http://en.wikipedia.org/wiki/On-board_diagnostics#cite_note-3
[19] http://en.wikipedia.org/wiki/IEEE_12207
[20] http://www.chinavasion.es/wifi-obdii-diagnostics-tool-apple-ipad-iphone-ipod-touc-p-
1757.html
[21]
https://docs.google.com/viewer?url=http://www.elmelectronics.com/DSheets/ELM322DS.pdf
&embedded=true&chrome=true
[22] http://www.kwp2000.info/supported_cars

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[23] http://en.wikipedia.org/wiki/Controller_area_network,
https://docs.google.com/viewer?url=http://focus.ti.com/lit/an/sloa101a/sloa101a.pdf&embed
ded=true&chrome=true, http://zone.ni.com/devzone/cda/tut/p/id/2732

Further Reading

http://www.google.com.mx/search?q=OBD&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-
US:official&client=firefox-a

http://de.wikipedia.org/wiki/ODX

http://www.cvel.clemson.edu/auto/systems/OBD.html

https://docs.google.com/viewer?url=http://www.vector.com/portal/medien/cmc/press/PDG/O
DX_HanserAutomotive_200612_PressArticle_EN.pdf&embedded=true&chrome=true

http://en.wikipedia.org/wiki/European_emission_standards

http://www.testing-expo.com/europe/07txeu_conf/pres/day_2/day_2_3.pdf

https://docs.google.com/viewer?url=http://www.vector.com/portal/medien/cmc/press/PDG/O
DX_HanserAutomotive_200612_PressArticle_EN.pdf&embedded=true&chrome=true

https://docs.google.com/viewer?url=http://www.autoshop101.com/forms/h46.pdf&embedded
=true&chrome=true

http://www.epa.gov/obd/questions.htm

http://www.epa.gov/obd/regtech/heavy.htm – OBD not yet required for heavy duty vehicles.

http://en.wikipedia.org/wiki/On-board_diagnostics

http://www.iqpc.com/Event.aspx?id=475354

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http://en.wikipedia.org/wiki/On-board_diagnostics#EOBD

http://www.epathchina.com/citroen-and-peugeot-on-board-diagnostic-system-p-51.html

In the U.S. various states have requirements, California being the traditional leader, here.
e.g.: http://www.arb.ca.gov/msprog/obdprog/obdprog.htm,
http://www.deq.virginia.gov/mobile/mobobd.html,
https://docs.google.com/viewer?url=http://www.anr.state.vt.us/air/airtoxics/docs/onboarddia
gnosticspamphlet.pdf&embedded=true&chrome=true,
http://www.tn.gov/environment/apc/vehicle/obd.shtml

https://docs.google.com/viewer?url=http://www.elmelectronics.com/DSheets/ELM322DS.pdf
&embedded=true&chrome=true

http://www.obd-codes.com/faq/obd-ii-protocols.php

http://www.permoveo.ltd.uk/TechnicalResources/EOBDOBD2Whatsthedifference.aspx

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Appendix – Automotive diagnostic 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
• J2411 - Describes the GMLAN (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 - Defines a data protocol for heavy duty commercial vehicles

ISO standards
• ISO 9141: Road vehicles — Diagnostic systems. International Organization for
Standardization, 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

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

Taken directly from: http://en.wikipedia.org/wiki/On-board_diagnostics#cite_note-3

This does not include the current ODX standard ISO 22901-1:2008.

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Automotive Diagnostic Systems - From OBD to Open Diagnostics Exchange format

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