| Level | Subfunction (req/resp) | Who Has Access | Typical Services |
|---|---|---|---|
| Level 1 | 0x01/0x02 | Workshop tools (dealer + independent) | WriteDID, IO control, ClearDTC, RoutineControl standard |
| Level 2 | 0x03/0x04 | OEM reprogramming tools only | RequestDownload, TransferData, erase routines |
| Level 3 | 0x05/0x06 | Engineering / development tools only | ReadMemoryByAddress (all ranges), raw I/O, bypass diagnostics |
| Development-only | 0x61/0x62 (OEM-specific) | R&D only; not shipped in production firmware | Unrestricted memory access, test modes |
Security Level Design Principles
Service-to-Security-Level Access Matrix
XMLDcm_AccessMatrix.arxml
0xF190
DefaultSession ExtendedDiagnosticSession
NoSecurityAccess
0x0101
DefaultSession ExtendedDiagnosticSession
ExtendedDiagnosticSession
SecurityLevel1
0xFF00
ProgrammingSession
SecurityLevel2
0x80F00000--0x80FFFFFF
ExtendedDiagnosticSession
SecurityLevel1
Production vs Development Security Configurations
⚠️ Development Security Levels in Production Firmware
Engineering-only security levels (0x61/0x62) that bypass normal access controls must be removed or permanently disabled before production firmware release. The most common security gap: development firmware with an 'always-unlock' debug level shipped in production through a process failure (wrong build variant flashed at EOL). Mandated controls: (1) build-time compiler flag disables all dev-only security levels in RELEASE build; (2) production firmware validation test confirms dev level returns NRC 0x35 (invalid key) on every attempt; (3) sign-off in release checklist.
Summary
Security level design is a risk management decision: Level 1 (workshop) must be accessible to independent repairers (EU Regulation 2018/858 mandates access), Level 2 (reprogramming) must be OEM-controlled to prevent unauthorized firmware flashing. The access matrix in DCM ARXML is the single source of truth — every service, every DID, every routine maps to exactly one (session, security level) combination. Test the access matrix systematically: verify every service returns the correct NRC for every incorrect (session, level) combination, not just the happy path.
🔬 Deep Dive — Core Concepts Expanded
This section builds on the foundational concepts covered above with additional technical depth, edge cases, and configuration nuances that separate competent engineers from experts. When working on production ECU projects, the details covered here are the ones most commonly responsible for integration delays and late-phase defects.
Key principles to reinforce:
- Configuration over coding: In AUTOSAR and automotive middleware environments, correctness is largely determined by ARXML configuration, not application code. A correctly implemented algorithm can produce wrong results due to a single misconfigured parameter.
- Traceability as a first-class concern: Every configuration decision should be traceable to a requirement, safety goal, or architecture decision. Undocumented configuration choices are a common source of regression defects when ECUs are updated.
- Cross-module dependencies: In tightly integrated automotive software stacks, changing one module's configuration often requires corresponding updates in dependent modules. Always perform a dependency impact analysis before submitting configuration changes.
🏭 How This Topic Appears in Production Projects
- Project integration phase: The concepts covered in this lesson are most commonly encountered during ECU integration testing — when multiple software components from different teams are combined for the first time. Issues that were invisible in unit tests frequently surface at this stage.
- Supplier/OEM interface: This is a topic that frequently appears in technical discussions between Tier-1 ECU suppliers and OEM system integrators. Engineers who can speak fluently about these details earn credibility and are often brought into critical design review meetings.
- Automotive tool ecosystem: Vector CANoe/CANalyzer, dSPACE tools, and ETAS INCA are the standard tools used to validate and measure the correct behaviour of the systems described in this lesson. Familiarity with these tools alongside the conceptual knowledge dramatically accelerates debugging in real projects.
⚠️ Common Mistakes and How to Avoid Them
- Assuming default configuration is correct: Automotive software tools ship with default configurations that are designed to compile and link, not to meet project-specific requirements. Every configuration parameter needs to be consciously set. 'It compiled' is not the same as 'it is correctly configured'.
- Skipping documentation of configuration rationale: In a 3-year ECU project with team turnover, undocumented configuration choices become tribal knowledge that disappears when engineers leave. Document why a parameter is set to a specific value, not just what it is set to.
- Testing only the happy path: Automotive ECUs must behave correctly under fault conditions, voltage variations, and communication errors. Always test the error handling paths as rigorously as the nominal operation. Many production escapes originate in untested error branches.
- Version mismatches between teams: In a multi-team project, the BSW team, SWC team, and system integration team may use different versions of the same ARXML file. Version management of all ARXML files in a shared repository is mandatory, not optional.
📊 Industry Note
Engineers who master both the theoretical concepts and the practical toolchain skills covered in this course are among the most sought-after professionals in the automotive software industry. The combination of AUTOSAR standards knowledge, safety engineering understanding, and hands-on configuration experience commands premium salaries at OEMs and Tier-1 suppliers globally.