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On-Board Diagnostics, or OBD, in an automotive context, is a generic term referring to a vehicle's self-diagnostic and reporting capability. The automotive industry is the industry involved in the design development manufacture marketing and sale of Motor vehicles In 2007 more than 73 million motor vehicles OBD systems give the vehicle owner or a repair technician access to state of health information for various vehicle sub-systems. The amount of diagnostic information available via OBD has varied widely since the introduction in the early 1980s of on-board vehicle computers, which made OBD possible. Early instances of OBD would simply illuminate a malfunction indicator light, or MIL, if a problem were detected—but would not provide any information as to the nature of the problem. Modern OBD implementations use a standardized fast digital communications port to provide realtime data in addition to a standardized series of diagnostic trouble codes, or DTCs, which allow one to rapidly identify and remedy malfunctions within the vehicle. OBD-II PIDs On Board Diagnostics "Parameter IDs" are codes used to request data from a vehicle used as a diagnostic tool

Contents

History

Standard interfaces

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 California, and denying registration to vehicles that did not pass, drivers would tend to purchase vehicles that would more reliably pass the test. California ( is a US state on the West Coast of the United States, along the Pacific Ocean. Along these lines, OBD-I was largely unsuccessful—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 effectively implement the annual testing program.

OBD 1. 5

"OBD 1. 5" is a slang term referring to a partial implementation of OBD-II which GM used on some vehicles in 1994 and 1995 (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. ) This hybrid system was present on the H-body 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 / Chevrolet 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 (Buick Skylark, Oldsmobile Achieva, Pontiac Grand Am) in 95. The Buick Regal is a Mid-size car produced by General Motors ' Buick division from 1973 through 2004 during which Buick also used the Century This is the article about the Lumina sedan and Coupe. For the Lumina minivan see Chevrolet Lumina APV. The Chevrolet Monte Carlo was an American-made automobile Originally introduced by Chevrolet for the 1970 model year (as competition with the Ford Thunderbird The Pontiac Grand Prix was an automobile that was produced by the Pontiac division of General Motors. The Oldsmobile Cutlass Supreme was a mid-size car produced by General Motors for the American market The Chevrolet Beretta was a Front wheel drive Coupé produced by the Chevrolet division of General Motors from 1987 through 1996 The Chevrolet Corsica is a Front-wheel drive mid-sized Automobile that was produced by General Motors from 1987 to 1996 The Chevrolet Corvette is a Sports car that has been manufactured by General Motors since 1953 The Chevrolet Camaro is a " Pony car " made in North America by the Chevrolet Motor Division of General Motors. The Pontiac Firebird was a Pony car built by the Pontiac division of General Motors between 1967 and 2002 The Chevrolet Cavalier was Chevrolet 's version of the compact GM J platform. The Pontiac Sunfire was introduced in the 1995 Model year as the Compact car to replace the Sunbird. The Buick Skylark was a passenger car produced by the Buick division of General Motors. Overview The Oldsmobile Achieva was introduced in 1992 and was a Front-wheel drive Compact car based on the GM N platform with Pontiac The Pontiac Grand Am was originally a Mid-size car and later a Compact car that was produced by the Pontiac division of General Motors.

Depending on the year and the vehicle, a car with the OBD 1. 5 system may have either the older OBD-I connector, or the newer OBD-II connector, but they are electrically identical to each other. For example, the 94-95 Corvettes have one post-cat oxygen sensor (although they have two catalytic converters), and have a subset of the OBD-II codes implemented. For a 1994 Corvette the implemented OBD-II codes are P0116-P0118, P0131-P0135, P0151-P0155, P0158, P0160-P0161, P0171-P0175, P0420, P1114-P1115, P1133, P1153 and P1158. [1]

The pinout for the ALDL connection on these cars is as follows:
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 battery voltage.

Additional vehicle-specific diagnostic and control circuits are 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. [2]

An OBD1. 5 has also been used on Mitsubishi cars of '95 '97 vintage.

An OBD1. 5 has been used in some 1995 Volkswagen VR6's (Juice Box's GTI)

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. 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 simplification of reporting diagnostic data led the feasibility of the comprehensive emissions testing program envisioned by the CARB.

OBD-II Diagnostic connector

Connector
Connector

The OBD-II specification provides for a standardized hardware interface—the female 16-pin (2x8) J1962 connector. Unlike the OBD-I connector, which was sometimes found under the hood of the vehicle, the OBD-II connector is nearly always located on the driver's side of the passenger compartment near the center console. SAE J1962 defines the pinout of the connector as:

  1. -
  2. Bus positive Line of SAE-J1850
  3. -
  4. Chassis ground
  5. Signal ground
  6. CAN high (ISO 15765-4 and SAE-J2234)
  7. K line of ISO 9141-2 and ISO 14230-4
  8. -
  9. -
  10. Bus negative Line of SAE-J1850
  11. -
  12. -
  13. -
  14. CAN low (ISO 15765-4 and SAE-J2234)
  15. L line of ISO 9141-2 and ISO 14230-4
  16. Battery voltage

The assignment of unspecified pins is left to the vehicle manufacturer's discretion. SAE International (SAE is a professional organization for mobility engineering professionals in the Aerospace, Automotive, and commercial Vehicle industries SAE International (SAE is a professional organization for mobility engineering professionals in the Aerospace, Automotive, and commercial Vehicle industries SAE International (SAE is a professional organization for mobility engineering professionals in the Aerospace, Automotive, and commercial Vehicle industries

Signal protocols

There are five signalling protocols currently in use with the OBD-II interface. Any given vehicle will likely only implement one of the protocols. Often it is possible to make an educated guess about the protocol in use based on which pins are present on the J1962 connector:

Note that pins 4 (battery ground) and 16 (battery positive) are present in all configurations. Also, ISO 9141 and ISO 14230 use the same pinout, thus the connector shape does not distinguish between the two.

Diagnostic data available

OBD-II provides access to numerous data from the ECU (Electronic Control Unit) and offers a valuable source of information when troubleshooting problems inside a vehicle. In automotive electronics an electronic control unit (ECU also called a Control unit, or Control module, is an Embedded system that controls one or more 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. SAE International (SAE is a professional organization for mobility engineering professionals in the Aerospace, Automotive, and commercial Vehicle industries 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 formulae 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 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 Individual manufactures often enhance the OBD-II code set with additional proprietary DTCs.

EOBD

EOBD is a version of OBD-II required in Europe since Model Year 2004 for diesel vehicles and since 2001 for gasoline vehicles[3]

EOBD2

The term "EOBD2" is a marketing term used by some vehicle manufacturers to refer to manufacturer-specific features that are not actually part of the ODB or EOBD standard. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum A marketing term is a term invented to promote the sales of a product [4] In this case "E" stands for european.

Scan tools

OBD scan tools can be categorized in several ways ranging from whether they are O. E. M. tools or aftermarket tools, whether they require a computer to operate (stand-alone tool vs PC-based software), and the intended market (professional or hobby/consumer use).

The advantages of PC-based scan tools are:

The advantages of stand-alone tools:

See List of Standalone OBD-II Scan Tools, List of OBD-II Cables & Scanning Software, and List of OBD-II Gauges & Performance Monitors.

Mode of Operation

Here is a basic introduction to the OBD communication protocol:

Mode $01 is used to identify what Powertrain information is available to the scan tool. In the field of Telecommunications, a communications protocol is the set of standard rules for data representation signaling authentication and error detection required to

Mode $02 displays Freeze Frame data.

Mode $03 lists the total number of powertrain or emission related DTC stored. It also displays exact numeric, 5 digit codes identifying the faults.

Mode $04 is used to clear DTCs and Freeze Frame.

Mode $05 displays the oxygen sensor monitor screen and the test results gathered about the oxygen sensor.

There are ten numbers available for diagnostics:

  1. $01 Rich-to-Lean O2 sensor threshold voltage
  2. $02 Lean-to-Rich O2 sensor threshold voltage
  3. $03 Low sensor voltage threshold for switch time measurement
  4. $04 High sensor voltage threshold for switch time measurement
  5. $05 Rich-to-Lean switch time in ms
  6. $06 Lean-to Rich switch time in ms
  7. $07 Minimum voltage for test
  8. $08 Maximum voltage for test
  9. $09 Time between voltage transitions in ms

Mode $06 is a Request for On-Board Monitoring Test Results for Non-Continuously Monitored System. There are typically a minimum value, a maximum value, and a current value for each non-continuous monitor.

Mode $07 is a Request for continuously Monitored 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.

There are only three continuous monitors to be identified: fuel, misfire, and the comprehensive component.

Mode $08 could enable the off-board test device to control the operation of an on-board system, test, or component.

Mode $09 is used to deliver IUMPR. (In Use Monitor Performance Ratio)

Mode $0A is required to store Permanent DTCs as per CARB.

Software Required

Many of the scan tools require a "host" computer, such as a laptop computer. A laptop computer, also known as a notebook computer, is a small Personal computer designed for mobile use.

Some come with proprietary software for Microsoft Windows. Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. Some require additional payment. See List of OBD-II Cables & Scanning Software

Free/open source software is available[5] for Linux and other Unix-like operating systems. Free and open source software, also F/OSS, FOSS, or FLOSS (for Free/Libre/Open Source Software) is software which is liberally licensed An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination

Standards documents

SAE standards documents on OBD-II

ISO standards

References

  1. ^ (Dec. , 1993) 1994 Corvette Service Manual, Book 2. General Motors Corporation, pp. 6E3-A-166 : 6E3-A-223.  
  2. ^ (Dec. , 1993) 1994 Corvette Service Manual, Book 2. General Motors Corporation, p. 6E3-A-11.  
  3. ^ KBM Systems - OBD Specifications :: OBD Introduction
  4. ^ KBM Systems - OBD Specifications :: OBD Introduction
  5. ^ Freediag - Vehicle Diagnostic Suite

See also

External links

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