Overview
ISO 14230-3:1999 - Road vehicles - Diagnostic systems - Keyword Protocol 2000 (KWP2000) - Part 3: Application layer defines how on-board Electronic Control Units (ECUs) and an off‑board tester exchange diagnostic services over the KWP2000 data link. It specifies the application‑layer implementation of the diagnostic services described in ISO 14229, including byte‑encoding, hexadecimal service identifiers, parameter encoding for requests/responses, and standard parameter values. The standard applies to vehicle setups with one or more ECUs connected (directly or via gateways) to a tester temporarily attached to the diagnostic data link.
Key topics and technical requirements
- Application‑layer mapping: Defines how diagnostic services map to the OSI model and how the application layer interacts with the KWP2000 data link.
- Diagnostic service implementation: Specifies the implementation rules for ISO 14229 diagnostic services, including mandatory/optional parameters and response handling.
- Byte‑encoding and hex values: Establishes encoding conventions for service identifiers, request/response parameters, and standard parameters (in hexadecimal).
- Message formats and flow: Describes request/response message structures, header conventions, checksum usage, and message‑flow examples for physical and functional addressing.
- Service families covered: Diagnostic Management (Start/Stop sessions, SecurityAccess, ECUReset, TesterPresent), Data Transmission (Read/Write by local/common identifier, memory access), Stored Data (DTC read/clear, freeze frame), I/O Control, Routine control, Upload/Download, and an extended EscapeCode service.
- Response codes and handling: Defines positive/negative response conventions, value ranges, and when/why specific response codes are returned.
- Implementation rules and examples: Includes parameter definitions, functional tables, message examples and application examples for multi‑ECU scenarios.
Practical applications
- Implementation blueprint for automotive diagnostic tools (conformance of off‑board testers to KWP2000 application layer).
- ECU firmware development to ensure correct diagnostic service handling and interoperability.
- Aftermarket diagnostic scanner vendors implementing protocol stacks and service identifiers.
- Vehicle service operations that rely on standardized diagnostic messaging to read DTCs, perform resets, run routines, upload/download calibration data, and manage secure access.
- Test labs and OEM verification teams using the standard to validate diagnostic communication behavior.
Who should use this standard
- Automotive software and firmware engineers (ECU and diagnostic tool development)
- Diagnostic-tool manufacturers and aftermarket vendors
- OEM diagnostic architects and integration engineers
- Vehicle service tool integrators and test engineers
- Regulatory and compliance specialists referencing standardized diagnostic behavior
Related standards
- ISO 14229 (Diagnostic services specification) - normative reference for service definitions
- ISO 14230-1 (Physical layer), ISO 14230-2 (Data link layer) - other parts of KWP2000
- ISO 14230-4 (Emissions-related requirements), SAE J1979, SAE J1930 - related automotive diagnostic references
For implementation, use ISO 14230-3 together with ISO 14229 and the KWP2000 physical/data link parts to achieve full, standards‑compliant diagnostic communication.