ISO 15031-4:2014

Overview

ISO 15031-4:2014 - "Road vehicles - Communication between vehicle and external equipment for emissions-related diagnostics - Part 4: External test equipment" - defines how external test equipment (including scan tools) must communicate with OBD-equipped vehicles for emissions-related diagnostics. The standard specifies a means of establishing communications and a set of diagnostic services that external test equipment must provide to exercise the vehicle services defined in ISO 15031-5. It ensures complete, efficient, and safe access to public OBD services on any compliant vehicle while allowing additional non-adverse capabilities in test tools.

Key topics and technical requirements

• OBD communication and protocols: Guidance for establishing interfaces over common vehicle bus systems and protocols (references include ISO 14230-4/DoK-Line, ISO 9141-2, ISO 15765-4/CAN, SAE J1850).
• Network access and message handling: Automatic interface determination, multiple tester communication, no-response and multiple-response handling, and message structure requirements.
• Diagnostic services for external equipment: Required services provided by scan tools to exercise ISO 15031-5 emissions-related diagnostic services (reading live data, freeze-frame data, test parameters, and results).
• DTC monitoring and code clearing: Procedures for reading, displaying and clearing diagnostic trouble codes (DTCs) and related emissions-monitor information.
• User interface and displays: Recommended displays and user input requirements (see Annex A) to present OBD emissions-related current data and freeze-frame data.
• Power, EMC and safety: Vehicle battery voltage/current support, electromagnetic compatibility (EMC) considerations (see ISO 7637-2 referenced), and design responsibility to prevent adverse effects on vehicle or tester.
• Conformance testing and annexes: Rules for conformance testing and normative/ informative annexes for protocol initialization and UI recommendations.

Practical applications

• Development and certification of scan tools and external diagnostic testers for passenger cars, light, medium and heavy-duty trucks subject to OBD regulations.
• Implementation guidance for aftermarket diagnostic tool vendors, vehicle OEM service equipment teams, emissions testing labs, and regulatory compliance testing bodies.
• Reference for diagnostic software engineers integrating OBD services, message handling, and protocol support into diagnostic applications.

Who should use ISO 15031-4

• Automotive diagnostic tool manufacturers and software developers
• Vehicle OEM service equipment designers
• Emissions laboratories and vehicle inspection agencies
• Regulatory bodies defining OBD compliance and test procedures

Related standards

• ISO 15031 series (Parts 1–7), especially ISO 15031-5 (Emissions-related diagnostic services), ISO 15031-2, ISO 15031-3, ISO 15031-6
• ISO 14230 (Keyword Protocol 2000), ISO 9141-2, ISO 15765-4 (DoCAN/CAN), ISO 7637-2 (EMC) and SAE documents (J1979, J1930, J2012) used for data and DTC definitions.

Keywords: ISO 15031-4, OBD, external test equipment, scan tool, on-board diagnostics, vehicle communication, emissions-related diagnostics, diagnostic trouble codes (DTCs).