全球統一的重型發動機的車載診斷系統（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，重型車輛應用車載診斷系統有兩種通訊協議：ISO 15765-4:2005 以及 SAE J1939-73。
在某些締約方法規中，這兩個通訊協議都可以使用，並且在將來的一段時間內會並行存在。
但是，在 2002 年 12 月 6-7號的會議上，WWH-OBD（重型發動機的車載診斷系統）工作小組決定，在汽車行業中，最終只會采取一種協議。
因此，WWH-OBD小組的一個分支小組起草了一套車載診斷系統通訊協議的一般性能標准，適用於重型車輛，該標准不僅可以滿足立法者的需求，還可以滿足維修人員的檢查與維修需求。
一同起草的還有該標准的草案完成時間表，該時間表已經交給 ISO TC22 SC3。
ISO標准27145是經ISO TC22 SC3審議后的結果。該標准涵蓋了基於以太網的TCP/IP 協議的車載到非車載的有線通訊的規定。
以太網上的TCP/IP協議為業界提供了更快的數據傳輸速度，也為將來的無線傳輸奠定了基礎，這也與某些締約方的道路傳輸的政策目標相符。
如上所述，世界范圍內的重型汽車平台上目前可以適用兩種通訊協議：ISO 15765-4:2005 以及 SAE J1939-73。
目前，歐洲的重型汽車車載診斷系統兼容兩種協議，
但是 2005/78/EC法令指出，當項目完成時，歐盟將考慮轉向使用 ISO 27145 標准。
在美國，現行和預計實行的車載診斷系統法規兼容兩種通訊協議。
車輛通訊平台非常復雜，並在汽車工業的幾乎各個方面都發揮着作用，包括開發、生產、修理以及檢測。因此，轉向使用 ISO 27145 標准對業界並非易事，
因為它將對開發、硬件和軟件方面的開支造成巨大影響。
因此，污染與能源工作組（GRPE）采納了WWH-OBD工作組的建議，在本全球性技術法規中采用步進式的方法來使用這個通用標准。
在本法規應用的最初使用階段，締約方將接受ISO/PAS 27145（基於 CAN）、SAE J1939-73（但應認識到，這些標准必須調整到完全符合本法規的標准）
或者 ISO 27145（基於 TCP/IP）的使用。