全球统一的重型发动机的车载诊断系统（WWH-OBD）
ISO/PAS 27145 is intended to become the single communication standard for access to OBD-related information.
To allow for a smooth migration from the existing communication standards to this future world-wide standardized communication standard,
the initial communication concept will be based on CAN.
In a second step, ISO/PAS 27145 will be extended to define the world-wide harmonized OBD communication standard based
on existing industry communications standards (e.g. Internet Protocol) over Ethernet.
Due to the usage of standard network layer protocols, future extensions to optional physical layers (e.g. wireless) are possible.
ISO/PAS 27145:2006 gives an overview of the structure and the partitioning of the different parts of ISO/PAS 27145,
and shows the relation between the parts. In addition, it outlines the use case scenarios where the ISO/PAS 27145 document set will be used.
All terminology that is common throughout the ISO/PAS 27145 document set is also outlined here.
ISO 27145-4:2012 defines the requirements to successfully establish, maintain and terminate communication
with a vehicle that implements the requirements of the World-Wide Harmonized On-Board Diagnostic Global
Technical Regulations (Global technical regulation No. 5).
This requires plug and play communication capabilities for the vehicle as well as for any test equipment that intends
to establish communication with a vehicle.
ISO 27145-4:2012 details all the OSI layer requirements to achieve this goal.
ISO 27145-4:2012 is intended to become the single communication standard for access to information relating to vehicle on‑board diagnostics (VOBD).
To allow for a smooth migration from the existing communication standards to this future world-wide standardized communication standard,
the communication concept as specified in ISO 27145-4:2012 is based on two different data links:
- · Diagnostic communication over Controller Area Network (DoCAN), ISO 15765-4;
- · Diagnostic communication over Internet Protocol (DoIP), ISO 13400 (all parts).
Use cases deriving from country-specific implementation of Global Technical Regulation No. 5 into local legislation are not included in ISO 27145-4:2012.
ISO 27145 – Basics of communication protocol
• Session layer uses UDS-protocol ISO 14229
• Transport layer DoCAN (Diagnostics over CAN) uses ISO 15765 CAN protocol
• Alternatively ISO 13400 DoIP (Diagnostics over IP) can be used as transport layer
• Data objects are widely compatible to SAE J1979, SAE J1939
• SAE J1979 identifiers for Mode 1, 6, 9 can be mapped onto Legacy Identifiers in ISO 27145
• SAE J1939 parameter groups can be mapped onto Legacy Identifiers in ISO 27145
Enhanced requirements for fault memory
• Diagnostic trouble code expanded to 3 bytes
• Diagnostic trouble code can be encoded as DTC according to SAE J2012 / ISO 15031-6 SPN according to SAE J1939-73 Unified DTC
• Distinction of Confirmed and Active DTC, Previously Active DTC, Pending DTC and Potential DTC
• Malfunction classification by severity class A, B1, B2, C
• OBD information shall not be erased by disconnection of the vehicle's battery
• Enhanced MI activation schemes
Important highlights of WWH-OBD
Introduction of WWH-OBD for trucks already by the end of 2012
ISO 27145 uses UDS protocol on ISO-CAN, which is quite often implemented in the ECU
Data objects can be handled like J1979 or J1939 data objects
Error manager and DTC output contains considerable enhancements(GTR fault status, malfunction classification and MI activation)
Permanent DTCs are not required by legislation
Conformance test is currently not required by legislation
目前，重型车辆应用车载诊断系统有两种通讯协议：ISO 15765-4:2005 以及 SAE J1939-73。
在某些缔约方法规中，这两个通讯协议都可以使用，并且在将来的一段时间内会并行存在。
但是，在 2002 年 12 月 6-7号的会议上，WWH-OBD（重型发动机的车载诊断系统）工作小组决定，在汽车行业中，最终只会采取一种协议。
因此，WWH-OBD小组的一个分支小组起草了一套车载诊断系统通讯协议的一般性能标准，适用于重型车辆，该标准不仅可以满足立法者的需求，还可以满足维修人员的检查与维修需求。
一同起草的还有该标准的草案完成时间表，该时间表已经交给 ISO TC22 SC3。
ISO标准27145是经ISO TC22 SC3审议后的结果。该标准涵盖了基于以太网的TCP/IP 协议的车载到非车载的有线通讯的规定。
以太网上的TCP/IP协议为业界提供了更快的数据传输速度，也为将来的无线传输奠定了基础，这也与某些缔约方的道路传输的政策目标相符。
如上所述，世界范围内的重型汽车平台上目前可以适用两种通讯协议：ISO 15765-4:2005 以及 SAE J1939-73。
目前，欧洲的重型汽车车载诊断系统兼容两种协议，
但是 2005/78/EC法令指出，当项目完成时，欧盟将考虑转向使用 ISO 27145 标准。
在美国，现行和预计实行的车载诊断系统法规兼容两种通讯协议。
车辆通讯平台非常复杂，并在汽车工业的几乎各个方面都发挥着作用，包括开发、生产、修理以及检测。因此，转向使用 ISO 27145 标准对业界并非易事，
因为它将对开发、硬件和软件方面的开支造成巨大影响。
因此，污染与能源工作组（GRPE）采纳了WWH-OBD工作组的建议，在本全球性技术法规中采用步进式的方法来使用这个通用标准。
在本法规应用的最初使用阶段，缔约方将接受ISO/PAS 27145（基于 CAN）、SAE J1939-73（但应认识到，这些标准必须调整到完全符合本法规的标准）
或者 ISO 27145（基于 TCP/IP）的使用。