OBDonUDS - SAE J1979-2


In almost all road vehicles, compliance with emission limits is monitored continuously and over the entire life cycle by means of on-board diagnostics (OBD) as required by law. The SAE J1979 standard describes in detail how the OBD data can be easily read out from the vehicle using an external diagnostic device ("scan tool"). All emission-related ECUs must provide corresponding diagnostic functionalities.

The freshly updated revision of the SAE J1979-2 standard (OBDonUDS) now requires the use of UDS (Unified Diagnostic Services) for reading out OBD diagnostic data. UDS is standardized in ISO 14229 and has been used for the extended, manufacturer-specific scope of diagnostics for many years.

In the past, different OBD standards (OBD II, Heavy Duty OBD (HD-OBD), World Wide Harmonized OBD (WWH-OBD)) have emerged for different vehicle categories (cars, motorcycles, light and heavy trucks, construction equipment) in different markets. It is expected that the new OBDonUDS standard will gradually replace these variants in the upcoming years.

OBDonUDS - J1979-2


Why was the OBD Standard Revised?

OBDonUDS - the next generation OBD protocol
OBDonUDS - the next generation OBD protocol

The revision of the diagnostic protocol became necessary because no more unique identifiers were available in several places due to length restrictions, e.g. for DTCs (trouble codes). Especially for the fault memory, data structures have been extended to allow more details on individual faults to be read (e.g. extended snapshot data). In addition, it is now possible to read out for each monitor how often it was actually executed in real driving operation (redesigned IUMPRs = In-Use Monitor Performance Ratio. Parameters for checking diagnostic frequency). In general, it is now possible to read out more and more qualified information on emission-relevant components.

Why is the New OBD Standard Based on the UDS Protocol?

UDS is an established and field-proven standard for manufacturer-specific diagnostics. AUTOSAR software components and many different tools are available for this purpose. Therefore, UDS is an excellent starting point for vehicle diagnostics required by legislation - the standard only needs to be extended to include OBD-specific use cases. The key advantage is thus that there is now only one protocol for diagnostics, rather than two or different ones. Consequently, statutory OBD diagnostics is easier to combine with manufacturer-specific diagnostics, which in turn leads to a significant simplification of ECU software.

What are the Consequences of OBDonUDS for the Development of new ECUs?

At first glance, the previous OBD protocol resembled the UDS protocol, but in detail, the two protocols have many as well as major differences. In practice, the differences resulted in ECUs containing two independent protocol implementations, one for the OBD protocol and another for the UDS protocol. With OBDonUDS, this is no longer necessary. However, new software is required in ECUs to implement OBDonUDS.

In addition, a specification tool is needed to precisely specify the OBDonUDS content for an ECU, which is now even more closely interlinked with manufacturer-specific diagnostics. A new test tool is required to test and validate the OBD portion of the ECU software. The old scan tools no longer work, and new tools are needed here as well. Tool changes are also expected in relation to documentation and archiving.

Vector already offers a comprehensive tool chain for the new SAE standard OBDonUDS. This tool chain supports all phases of development, from specification of the relevant OBD content to implementation in ECU software and its validation, and finally to application in the OBD diagnostic tester ("scan tool").

Ready for a Brief Introduction to the New Standard?

Getting Started with OBDonUDS (SAE J1979-2) and showing a diagnostic scan tool demo for the standard with Indigo
OBDonUDS (SAE J1979-2) - brief overview about the new standard and related Vector Tools

OBDonUDS Tools & Services

Embedded Software
Integrate OBDonUDS into the ECU as comprehensive software components - also with manufacturer-specific adaptations MICROSAR OBD
Specify the exact diagnostic scope of OBDonUDS user-oriented for each individual system CANdelaStudio
Test and validate the implementation and integration of OBDonUDS fully automated in ECUs. CANoe.DiVa
Diagnostic Tester / OBD Scan Tool
Easily read and evaluate the OBDonUDS data from the vehicle - also in combination with the advanced, manufacturer-specific diagnostics Indigo
Connect the diagnostic tester to the vehicle with a compact network interface for Ethernet/BroadR-Reach and CAN VN0312
Engineering and Consulting
We support you in the efficient and productive implementation of OBDonUDS in workflows, data flows and ECU software. Services

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Max Beck
Helping to simplify the practical use of vehicle diagnostics.

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