This SAE Recommended Practice defines diagnostic test modes, and request and response messages, necessary to be supported by vehicle manufacturers and test tools to meet the requirements of the California OBD II and Federal OBD regulations, which pertain to vehicle emission-related data only. These messages are intended to be used by any service tool capable of performing the mandated diagnostics. In addition, capabilities are defined that are intended to meet other Federal and State regulations pertaining to related issues such as Inspection and Maintenance (I/M) and service information availability. This document provides the mechanism to satisfy requirements included in regulations, and not all capabilities included in this document are required by regulations. This document also is not considered a final authority for interpretation of the regulations, so the reader should determine the applicability of the capabilities defined in this document for their specific need. Diagnostic Test Modes included in this document are:

1. a Mode $01—Request Current Powertrain Diagnostic Data
   1. Analog inputs and outputs
   2. Digital inputs and outputs
   3. System status information
   4. Calculated values
2. b Mode $02—Request Powertrain Freeze Frame Data
   1. Analog inputs and outputs
   2. Digital inputs and outputs
   3. System status information
   4. Calculated values
3. c Mode $03—Request Emission-Related Powertrain Diagnostic Trouble Codes
4. d Mode $04—Clear/Reset Emission-Related Diagnostic Information
5. e Mode $05—Request Oxygen Sensor Monitoring Test Results
6. f Mode $06—Request On-Board Monitoring Test Results for Non-Continuously Monitored Systems
7. g Mode $07—Request On-Board Monitoring Test Results for Continuously Monitored Systems
8. h Mode $08—Request Control of On-Board System, Test, or Component
9. i Mode $09—Request Vehicle Information

For each test mode, this specification includes:

1. a Functional descriptions of test mode
2. b Request and response message formats

For some of the more complex test modes, an example of messages and an explanation of the interpretation of those messages is included.