Designing On-Board Diagnostics for Light and Medium Duty Emissions Control Systems

On-board diagnosis of engine and transmission systems has been mandated by government regulation for light and medium vehicles since the 1996 model year. The regulations specify many of the detailed features that on-board diagnostics must exhibit. In addition, the penalties for not meeting the requirements or providing in-field remedies can be very expensive. This course is designed to provide a fundamental understanding of how and why OBD systems function and the technical features that a diagnostic should have in order to ensure compliant and successful implementation.

Fundamental design objectives and features needed to achieve those objectives for generic on-board diagnostics will be covered. The course will also include a review of the California Air Resources OBD II regulation, providing students with a firm foundation for reading and understanding the requirements, including the in-use rate portion of the regulations and how to properly calculate and output the required rate information. Relationships between the regulation and various SAE and ISO recommended practices will be reviewed. The course will also explore the relationship of the OBD system with the underlying control system.

Note that because of proprietary considerations, this class does not provide details of algorithm design, algorithm performance, or algorithm application. The class will cover general OBD algorithm designs and the features required to promote sound OBD system design.

What Will You Learn

By attending this seminar, you will be able to:
  • Articulate the underlying design objectives of on-board diagnostic systems
  • Use the latest California Air Resources Board On-Board Diagnostic Regulation for Light and Medium Vehicles to find and apply OBD requirements
  • Apply the design features that all diagnostics need for successful implementation
  • Design diagnostics to comprehend variation
  • Successfully implement algorithms to track in-use rates in accordance with the CARB OBD II Regulation
  • Use SAE J1979 to implement generic scan tool support in diagnostic design
  • Implement OBD design requirements in control system design

Is This Course For You

This course is designed for engineers involved in either the design or control of on-board diagnostic systems for engines or transmissions for light and medium duty on-road vehicles. Individuals working in the heavy duty industry may also find the information interesting, but should note that the examples will be geared towards spark ignition engines and light and medium duty regulations. In addition, engineers involved in engine and transmission hardware will benefit by obtaining a better understanding of the design of OBD systems. Engineers new to the area of OBD system design and engineers involved in the design of control systems wishing to obtain a better understanding of OBD requirements will also find the course valuable.

Materials Provided

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Course Requirements

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  • Fundamental Design Objectives for OBD Systems
  • Basic Design Features for OBD Systems
  • Exercise: "Customers" and their OBD Requirements
  • Overview of the World Wide OBD Regulatory Structure
  • California Air Resources Board (CARB) Regulatory Process
  • How to use the CARB Light/Medium Regulation
    • Malfunction and diagnostic system requirements
    • Enforcement of malfunction and diagnostic system requirements
  • CARB Regulation - an in-depth look at:
    • In-use rates
    • Comprehensive component requirements
  • Introduction to a Diagnostic Design Process (Box, Graves, Bisgaard, Van Gilder, et al)
  • Defining "Good" vs. "Bad" Systems
  • Exercise: Defining Good vs. Defective Systems
  • Anatomy of an On-Board Diagnostic
  • Diagnostic Modeling
  • Exercise: Induction System Modeling
  • Understanding and Dealing with Variation
    • Decision making processes
    • Design guidelines for Exponentially Weighted Moving Averages (EWMA)
  • SAE J1979 - An Overview
  • Exercise: Finding Information in J1979
  • System Design for Diagnosibility
  • Overview of Regulatory Requirements Related to OBD
    • In-use Enforcement
    • Emissions warranty
  • OBD Certification Process
  • The Relationship between the Control and OBD System Design