1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.Copyright 2002 Society of Automotive Engineers, Inc.All rights reserved. No part of this
3、 publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying,recording, or otherwise, without the prior written permission of SAE.TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (o
4、utside USA)Fax: 724-776-0790Email: custsvcsae.orgSAE WEB ADDRESS: http:/www.sae.orgSURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICEJ1978REV.APR2002Issued 1992-03Revised 2002-04Superseding J1978 FEB1998OBD II Scan Tool Equivalent to ISO/DIS 15031-4:December 14, 2001T
5、his document supersedes SAE J1978 FEB1998, and is technically equivalent to ISO/DIS 15031-4:December 14,2001, except for minor reorganization of Paragraphs 1 and 2.ForewordOn-Board Diagnostic (OBD) regulations require passenger cars, and light and medium duty trucks, tosupport communication of a min
6、imum set of diagnostic information with off-board “generic” test equipment. Thisdocument describes the minimum capabilities that must be supported by test equipment (e.g., handheld scantools, PC based diagnostic computers, etc.) that are intended to communicate with an OBD compliant vehicle toretrie
7、ve the OBD information.SAE J1978 was originally developed to meet U.S. OBD requirements for 1996 and later model year vehicles. ISO15031-4 was based on SAE J1978 and was intended to meet European OBD requirements for 2000 and latermodel year vehicles, and added the capability to communicate on an IS
8、O 15765-4 serial data link. This documentis technically equivalent to ISO 15031-4 with U.S. specific requirements identified.TABLE OF CONTENTS1. Scope . 31.1 Purpose 31.2 Differences from ISO Document. 32 Reference . 32.1 Applicable Publications 32.1.1 SAE Publications 32.1.2 ISO Publications . 42.2
9、 Related Publications . 42.2.1 ISO Documents 43. Terms and Definitions. 44. Required Functions of the External Test Equipment 45. Communication Protocols. 46. Connections to the Vehicle . 5SAE J1978 Revised APR2002-2-7. Network Access 57.1 Automatic Determination of Communication Interface57.2 Handl
10、ing of No Response from the Vehicle 77.3 Handling of Multiple Responses from the Vehicle 77.4 Message Structure 77.5 Diagnostic Trouble Codes Monitoring.77.6 Obtain and Display OBD Emissions Related Current Data, Freeze Frame Data,and Test Parameters and Results 77.7 Code Clearing 87.8 On-Board Diag
11、nostic Evaluations .87.8.1 Completed On-Board System Readiness Tests .87.8.2 Supported On-Board System Readiness Tests 87.8.3 Malfunction Indicator Lamp - Status and Control87.9 Use of StopCommunication Service Associated with ISO 14230-4 (optional) 88. User Interface .88.1 Display 88.2 User Input .
12、99. Power Requirements 99.1 Vehicle Battery Voltage 99.1.1 Vehicle Battery Voltage for 12 V DC only .99.1.2 Vehicle Battery Voltage for 12 V DC and 24 V DC .99.2 Vehicle Battery Current Consumption 1010 Electromagnetic Compatibility (EMC) . 1011 Conformance Testing . 1011.1 General .1011.2 Determine
13、 OBD Communication Type1111.3 On-Board System Readiness Test . 1211.4 Select Functions .1211.5 Select and Display Items 1211.6 Confirm Requests to Clear Codes 1311.7 General Diagnostic Communication Tests 1311.8 Capacitance and Impedance at the Diagnostic Connector. 1311.9 Operating Voltage and Curr
14、ent Requirement . 1311.10 Protocol Check . 1311.11 Alphanumeric Display . 1411.12 User Manual and Help Facility 1412 Notes 1412.1 Marginal Indicia. 14SAE J1978 Revised APR2002-3-1. Scope1.1 PurposeThis SAE Recommended Practice supersedes SAE J1978 FEB1998, and is technically equivalentto ISO/DIS 150
15、31-4:December 14, 2001.This document is intended to satisfy the requirements of an OBD scan tool as required by U.S. On-BoardDiagnostic (OBD) regulations. The document specifies:a. A means of establishing communications between an OBD-equipped vehicle and external testequipment,b. A set of diagnosti
16、c services to be provided by the external test equipment in order to exercise theservices defined in SAE J1979,c. Conformance criteria for the external test equipment.1.2 Differences from ISO DocumentThe ISO 15031-4 document is intended to satisfy the requirements ofOBD requirements in countries oth
17、er than the U.S., and includes functionality not required or not allowed in theU.S. Notable exceptions are:a. Proposed U.S. OBD regulations will allow ISO 15765-4 as an allowable OBD serial data link at500 kbps only. Only those provisions of ISO 15765-4 that pertain to 500 kbps are required to besup
18、ported by an SAE J1978 diagnostic scan tool.b. Proposed U.S. OBD regulations will not allow greater than 20 V at the SAE J1962 connector. Only theType A connector as defined in SAE J1962 needs to be supported by an SAE J1978 diagnostic scantool.Differences between the documents are highlighted in th
19、e technical requirements sections of this document.Deleted text is highlighted with struck through and new text is highlighted with bold italic.NOTE To maintain equivalency of the documents, a comma is used as a decimal marker for numericvalues in this document.2. References2.1 Applicable Publicatio
20、nsThe following publications form a part of this specification to the extent specifiedherein. Unless otherwise indicated, the latest version of SAE publications shall apply.2.1.1 SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J1850 MAY2001Class B Data Commu
21、nications Network Interface.SAE J1930Electrical/Electronic Systems Diagnostic Terms, Definitions, Abbreviations, and Acronyms -Equivalent to ISO/TR 15031-2:April 30, 2002SAE J1962Diagnostic Connector - Equivalent to ISO/DIS 15031-3: December 14, 2001SAE J1979E/E Diagnostic Test Modes - Equivalent to
22、 ISO/DIS 15031-5:April 30, 2002SAE J2012Diagnostic Trouble Code Definitions - Equivalent to ISO/DIS 15031-6:April 30, 2002SAE J1978 Revised APR2002-4-2.1.2 ISO P UBLICATIONSAvailable from ANSI, 25 West 43rd Street, New York, NY 10036-8002.ISO 7637-1:1990Road vehicles Electrical disturbance by conduc
23、tion and coupling Part 1:Passenger cars and light commercial vehicles with nominal 12V supply voltage Electrical transientconduction along supply lines onlyISO 9141-2:1994Road vehicles Diagnostic systems Part 2: CARB requirements for interchange ofdigital informationISO 9141-2:1994/Amd.1:1996Road ve
24、hicles - Diagnostic systems Part 2: CARB requirements forinterchange of digital information Amendment 1.ISO 14230-4:2000Road vehicles Keyword protocol 2000 for diagnostic systems Part 4:Requirements for emission-related systemsISO/DIS 15031-4: December 14, 2001Road vehicles Communication between veh
25、icle and externaltest equipment for emissions-related diagnostics Part 4: External test equipmentISO 15765-4:2001Road vehicles Diagnostics on Controller Area Network (CAN) Part 4:Requirements for emissions-related systemsISO 16750-2Road vehicles Environmental conditions and testing for electrical an
26、d electronicequipment Part 2: Electrical loads2.2 Related PublicationThe following publication is provided for information purposes only and is not a requiredpart of this specification.2.2.1 ISO P UBLICATIONAvailable from ANSI, 25 West 43rd Street, New York, NY 10036-8002.ISO 15031-1:2001Road vehicl
27、es Communication between vehicle and external test equipment foremissions-related diagnostics Part 1: General information3. Terms and DefinitionsFor the purpose of this document the definitions of SAE J1930 apply.4. Required Functions of the External Test EquipmentThe following are the basic functio
28、ns that theexternal test equipment is required to support or provide: Automatic hands-off determination of the communication interface used to provide OBD services onthe vehicle, Obtaining and displaying the status and results of vehicle on-board diagnostic evaluations, Obtaining and displaying OBD
29、emissions related diagnostic trouble codes (DTCs), Obtaining and displaying OBD emissions related current data, Obtaining and displaying OBD emissions related freeze frame data, Clearing the storage of OBD emissions related diagnostic trouble codes, OBD emissions relatedfreeze frame data storage and
30、 OBD emissions related diagnostic tests status, Obtaining and displaying OBD emissions related test parameters and results as described in SAEJ1979, Provide a user manual and/or help facility.5. Communication ProtocolsThe following communication protocols shall be supported:a. ISO 9141-2The followin
31、g specifications clarify and, if in conflict with ISO 9141-2, override any relatedspecifications in ISO 9141-2: The maximum sink current to be supported by the external test equipment is 100 mA, The range for all tests performed relative to ISO 7637-1 is 1.0 to +40.0 V, The minimum bus idle period b
32、efore the external test equipment shall transmit an address, shall be300 ms.SAE J1978 Revised APR2002-5-b. SAE J1850 41,6 kbps PWM (pulse width modulation)c. SAE J1850 10,4 kbps VPW (variable pulse width)d. ISO 14230-4 (Keyword protocol 2000)e. ISO 15765-4 (CAN) NOTE: Proposed U.S. regulations will
33、allow ISO 15765-4 as an allowable OBD serial datalink at 500Kbps only. Only those provisions of ISO 15765-4 that pertain to 500 kbps arerequired to be supported by an SAE J1978 diagnostic scan tool.A fully compliant external test equipment shall support all communication protocols as specified in Se
34、ction 5.Only one protocol is allowed to be used in any one vehicle to access all legislated emission-related functions.The external test equipment is not required to support simultaneous use of protocols.6. Connections to the VehicleNOTE Proposed U.S. regulations will not allow greater than 20 V at
35、the SAE J1962 connector. Onlythe Type A connector as defined in SAE J1962 needs to be supported by an SAE J1978diagnostic scan tool.Connection to the vehicle shall be made using the connector specified in SAE J1962. All data transfer betweenexternal test equipment and the vehicle shall conform to th
36、e requirements of SAE J1979.7. Network Access7.1 Automatic Determination of Communication InterfaceThe external test equipment shall have an“Automatic hands-off determination of the communication interface” built in to determine the communicationprotocol used in a given vehicle.The tests to determin
37、e the communication interface and protocol may be performed in any order and, wherepossible, may be performed simultaneously. The specified sequence for each test shall be used to determinethe interface to be used to access OBD services on a vehicle:a. The electrical interface in the external test e
38、quipment for the manufacturer discretionary contactassignments shall be effectively open circuit as a default condition or state whilst this procedure isbeing performed.b. The equipment shall inform the user that initialization is occurring.c. The equipment shall, using only the following tests, att
39、empt to determine the OBD communicationsprotocol used by the vehicle. No user intervention is allowed during this stage.1. Test for SAE J1850 41,6 kbps (kilobits per second) PWM (pulse width modulation): enable the SAE J1850 41,6 kbps PWM interface; send a service $01 PID $00 request message; if a s
40、ervice $01 PID $00 response message is received then SAE J1850 41,6 kbps PWM is thevehicles OBD protocol.2. Test for SAE J1850 10,4 kbps VPW (variable pulse width): enable the SAE J1850 10,4 kbps VPW interface; send a service $01 PID $00 request message; if a service $01 PID $00 response message is
41、received then SAE J1850 10,4 kbps VPW is thevehicles OBD protocol.SAE J1978 Revised APR2002-6-3. Test for ISO 9141-2: enable the ISO 9141-2 interface; if the initialization sequence specified in ISO 9141-2 is completed successfully, then ISO 9141-2is the vehicles OBD protocol.4. Test for ISO 14230-4
42、: enable the ISO 14230-4 interface; if the initialization sequence specified in ISO 14230-4 is completed successfully, then ISO14230-4 is the vehicles OBD protocol.5. Test for ISO 15765-4: legacy vehicles previously were allowed to use the contacts now defined for CANcommunication as manufacturer di
43、scretionary. The external test equipment shall ensureadequate protection from these legacy signals, perform the “External Test Equipment Initialization Sequence” defined in ISO 15765-4, if the initialization sequence specified in ISO 15765-4 is completed successfully, then ISO15765-4 is the vehicles
44、 OBD protocol.The service $01 PID $00 request and response messages are specified in SAE J1979.Both ISO 9141-2 and ISO 14230-4 specify a time within which a module(s) that has successfully beeninitialized must receive a message or the module(s) will return to the address mode. Unless the external te
45、stequipment user has indicated he/she wishes to terminate communication, once a module(s) has successfullybeen initialized, the external test equipment must automatically send a message, to be identified as the idlemessage, before this time can elapse. Any use of any response received due to the idl
46、e message is at thediscretion of the external test equipment manufacturer. For vehicles using ISO 9141-2 service $01 PID $00 request shall be used as the idle message.For vehicles using ISO 14230-4 the service TesterPresent is the recommended way to satisfy the idlemessage requirement as specified i
47、n ISO 14230-4. Alternatively, the service $01 PID $00 as specified in SAEJ1979 may be used.If none of the protocol tests shown above succeeds, the equipment shall repeat all of them and advise theuser:a. That communication with the vehicle could not be established,b. To confirm that the ignition key
48、 is in the “ON” position,c. To check the emissions label or vehicle service information to confirm that the vehicle is OBDequipped,d. To confirm that the external test equipment is connected to the vehicle correctly.The equipment shall continue to repeat the protocol tests shown above until either o
49、ne of them passes or theuser chooses to abandon the attempt. The equipment may also indicate the number of failed initializationattempts to the user.SAE J1978 Revised APR2002-7-7.2 Handling of No Response from the VehicleA vehicle module may fail to respond to a request messagefrom the external test equipment because of incorrect transmission or because the module does not supportthat message. If a response is not received within the time-out period prescribed by the protocol, the externaltest equ
