Overview
ISO 22901-3:2018 - Road vehicles - Open diagnostic data exchange (ODX) - Part 3: Fault symptom exchange description (FXD) - defines a machine‑readable format for describing fault symptom algorithms implemented as diagnostic software in an ECU. The standard enables standardized exchange of diagnostic “raw information” from function and software suppliers to vehicle manufacturers (VMs) to support automated tool processing and downstream document generation (for example, OBD summary sheets and repair and maintenance information (RMI)). Primary benefits include improved efficiency and independence from supplier- or VM‑specific formats.
Key technical topics and requirements
- FXD concept and workflow: Formalizes the end‑to‑end process for delivering and using FXD data, including a traditional workflow and FXD‑based workflows for tool‑based processing.
- Machine‑readable FXD format: Defines an XML schema and versioning rules to capture fault symptom algorithms, associated calibration values and metadata.
- Raw information and data dictionaries: Supports DATA‑DECLARATIONS, COMPUTATIONS and UNIT‑SPEC definitions so diagnostic logic is unambiguous and reusable.
- Variable and state descriptions: Covers SIMPLE‑VARIABLE, BIT‑FIELD‑VARIABLE and STATE‑GRAPH constructs to represent ECU variables referenced by diagnostics.
- Fault symptom model: Formal elements for FAULT‑IDENTIFICATION, MON‑COMPONENT, FAULT‑CLASSIFICATION, FAULT‑DETECTIONS, RATIO‑GROUPS (for in‑use monitor performance), READINESS‑GROUPS and related items.
- Attributes and referencing: Standard attribute set (ID, ID‑REF, VERSION, HREF, xml:lang, etc.), variant coding, selection lists and external document references to enable consistent cross‑referencing and localization.
- Calibration and reuse mechanisms: Central calibration info, inheritance/value mechanisms, inhibitions, substitution and protective functions to support multiple variants and ECU configurations.
- Use cases and constraints: Formal use cases (delivery of raw info, document generation) and schema update constraints to preserve interoperability.
Practical applications and users
ISO 22901-3 (FXD) is used by:
- ECU function & software suppliers - to deliver standardized diagnostic symptom definitions to VMs.
- Vehicle manufacturers - to ingest supplier FXD for vehicle integration, type approval and documentation.
- Tool vendors - to build diagnostic, documentation‑generation and calibration tools that process FXD.
- Aftermarket and repair information providers - to generate RMI and service content automatically.
- Regulatory and approval bodies - to verify consistent OBD summary sheets and type‑approval documentation.
Key practical outcomes include automated generation of OBD summary sheets, harmonized repair instructions, improved tool interoperability and reduced manual format conversion efforts.
Related standards
- Part of the ISO 22901 ODX family (Open Diagnostic Data Exchange). FXD is complementary to other ODX parts that define exchange formats and broader diagnostic data models. Keywords: ISO 22901-3, ODX, FXD, ECU diagnostic data, vehicle diagnostics, OBD summary sheet, repair and maintenance information, diagnostic data exchange.
Open preview (PDF)Road vehicles — Open diagnostic data exchange (ODX) — Part 3: Fault symptom exchange description (FXD)
