Road vehicles — Unified diagnostic services (UDS) — Part 1: Application layer — Amendment 1
2Expert Interpretation
An in-depth analysis of the 11 technical updates of the Unified Diagnostic Service (UDS) application layer in the ISO 14229-1:2020/Amd.1:2022 standard, including core changes such as DTC state machine logic optimization, user-defined data record expansion, and memory address range adjustment, providing an implementation guide for automotive electronics engineers.
Background of Standard Revision
As the core standard in the field of on-board diagnostics, after the third edition of ISO 14229-1 was released in 2020, Amendment 1 was released in October 2022 to adapt to the evolution of ECU diagnostic requirements. This update mainly solves the following problems:
- The demand for user-defined fault memory (UserDefMemory) management has increased sharply
- The precise control requirements of the DTC state machine in the OBD scenario
- The problem of uniform naming standards for diagnostic service parameters
Core change analysis
Diagnostic memory range adjustment
Comparison of memory address range changes in Table 2:
| Parameter | Original range (hex) | New range (hex) |
|---|---|---|
| Standard memory segment | 8016-8216 | 8016-8316 |
| Extended memory segment | 8316-8816 | 8416-8816 |
After adjustment, the ECU needs to remap the memory space to ensure that the 8416-8316 range is reserved for future expansion.
DTC state machine optimization
Modification of confirmation threshold in clause D.2.1:
Before change: For non-OBD use cases, the default is 1 operation cycle to confirm the fault
After change: It is clarified that the confirmation threshold of non-OBD use cases can be set to 0, and a new TripCounter increment condition is added:
- testFailedThisOperationCycle=1 must be satisfied
- The operation cycle is fully executed
Implementation suggestions
Compatibility solution
- For ECU that uses the original memorySize>1 verification, it needs to be upgraded to >000016 verification
- DTCExtDataRecordNumber parameter processing needs to distinguish between standard and user-defined scenarios
- Added UserDefDTCExtDataRecordNumber range definition (see the table below)
| Value range | Purpose | Example scenario |
|---|---|---|
| 0016 | ISO/SAE reserved | Regulatory diagnosis |
| 0116-FE16 | Automaker customization | Battery management system log |
| FF16 | Read all records | Batch export of faults |
Technology Evolution Analysis
This revision reflects three major trends:
- Diagnosis refinement: DTC state machine adds operation cycle completion judgment conditions
- Expanded flexibility: UserDefMemory-related parameters account for 63%
- Terminology standardization: Unify the naming of parameters such as DTCExtDataRecord
It is recommended to update the transport layer implementation in conjunction with ISO 14229-3:2022.