| FMEA Type | Standard Reference | Purpose | Inputs |
|---|---|---|---|
| Design FMEA (DFMEA) | ISO 26262 Part 9 Clause 5 | Hardware design failure analysis | Schematic, BOM, hardware architecture |
| System FMEA | ISO 26262 Part 9 | System-level failure propagation | System architecture, FSC, TSRs |
| Software FMEA | ISO 26262 Part 9 | Software fault analysis (less common) | SW architecture, module interfaces |
| FMEA-MSR (Monitoring and System Response) | AIAG-VDA | Failure detection and response analysis | Diagnostic architecture |
FMEA Types in ISO 26262
FMEA Process: Five-Step Method
FMEA Process
Step 1: Define scope and boundaries
└── Which hardware/system elements to analyse?
Define failure mode classification hierarchy
Step 2: Identify failure modes for each element
└── For each component/function: how can it fail?
Common failure mode guide: short circuit, open circuit, stuck-at-high,
stuck-at-low, out-of-range, intermittent, delayed
Step 3: Determine effects of each failure mode
└── Local effect (on the component)
Next-higher-level effect (on the sub-system)
End effect (at vehicle / safety level) → link to hazardous event
Step 4: Assign Severity, Occurrence, Detection ratings
└── Severity (S): 1–10 (matches hazardous event severity)
Occurrence (O): 1–10 (estimated failure rate)
Detection (D): 1–10 (likelihood that diagnostic detects the fault)
RPN = S × O × D (Risk Priority Number; high RPN → priority for mitigation)
Step 5: Define mitigation actions
└── Design change (reduce occurrence)
Add diagnostic mechanism (reduce detection rating)
Add redundancy (reduce severity effect)
Re-assess RPN after actionsFMEA Worksheet for Hardware Component
| Component | Failure Mode | Local Effect | End Effect | S | O | D | RPN | Mitigation |
|---|---|---|---|---|---|---|---|---|
| Radar sensor supply (5V) | Open circuit (no output) | Sensor unpowered | No radar data; AEB disabled | 8 | 2 | 3 | 48 | Power monitor; DEM event; safe state |
| Radar sensor supply (5V) | Short to ground | Sensor unpowered; fuse blows | No radar data; AEB disabled | 8 | 1 | 2 | 16 | Fuse; power monitor |
| Radar CAN transceiver | Bus-off state | No CAN transmission | No radar object list | 8 | 2 | 2 | 32 | CAN timeout monitor; 50ms threshold; safe state |
| Radar CAN transceiver | CAN frame corruption | Garbled data | Wrong object detected; false AEB | 9 | 1 | 2 | 18 | CRC on CAN data (CRC-15); E2E protection |
| Torque sensor (EPS) | Stuck-at-zero | Zero torque reading | EPS gives full assistance when driver not steering | 9 | 1 | 2 | 18 | Redundant sensor channel; cross-check |
| MCU flash (ECC) | Single-bit error | Corrected by ECC | No effect (transparent) | 1 | 3 | 1 | 3 | ECC hardware; DEM log; schedule scrub |
| MCU flash (ECC) | Double-bit error | Uncorrectable read error | SW crashes or returns wrong value | 10 | 1 | 1 | 10 | ECC trap handler; safe state; DEM event |
Summary
FMEA is a bottom-up analysis: starting from component failure modes and propagating effects upward to the system level. It is complementary to FTA, which is top-down. The diagnostic coverage (DC) of each safety mechanism is the key output from FMEA: if a CAN timeout monitor detects 95% of radar communication failures, it has DC = 95%. ISO 26262 Part 5 uses this DC value to calculate the Single Point Fault Metric (SPFM) — a component failure mode with no diagnostic mechanism contributes its full failure rate to the residual risk, while one with 99% DC contributes only 1% of its failure rate.
🔬 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.