There are ten numbers available for diagnostics: $01 Rich-to-Lean O2 sensor threshold voltage $02 Lean-to-Rich O2 sensor threshold voltage $03 Low sensor voltage threshold for switch time measurement $04 High sensor voltage threshold for switch time measurement $05 Rich-to-Lean switch time in ms $06 Lean-to Rich switch time in ms $07 Minimum voltage for test $08 Maximum voltage for test $09 Time between voltage transitions in ms Service / Mode $06 is a Request for On-Board Monitoring Test Results for Continuously and Non-Continuously Monitored System. There are typically a minimum value, a maximum value, and a current value for each non-continuous monitor. Service / Mode $07 is a Request for emission-related diagnostic trouble codes detected during current or last completed driving cycle. It enables the external test equipment to obtain "pending" diagnostic trouble codes detected during current or last completed driving cycle for emission-related components/systems. This is used by service technicians after a vehicle repair, and after clearing diagnostic information to see test results after a single driving cycle to determine if the repair has fixed the problem. Service / Mode $08 could enable the off-board test device to control the operation of an on-board system, test, or component. Service / Mode $09 is used to retrieve vehicle information. Among others, the following information is available: VIN (Vehicle Identification Number): Vehicle ID CALID (Calibration Identification): ID for the software installed on the ECU CVN (Calibration Verification Number): Number used to verify the integrity of the vehicle software. The manufacturer is responsible for determining the method of calculating CVN(s), e.g. using checksum. In-use performance counters Gasoline engine : Catalyst, Primary oxygen sensor, Evaporating system, EGR system, VVT system, Secondary air system, and Secondary oxygen sensor Diesel engine : NMHC catalyst, NOx reduction catalyst, NOx absorber Particulate matter filter, Exhaust gas sensor, EGR system, VVT system, Boost pressure control, Fuel system. Service / Mode $0A lists emission-related "permanent" diagnostic trouble codes stored. As per CARB, any diagnostic trouble codes that is commanding MIL on and stored into non-volatile memory shall be logged as a permanent fault code. See OBD-II PIDs for an extensive list of this information. Applications Various tools are available that plug into the OBD connector to access OBD functions. These range from simple generic consumer level tools to highly sophisticated OEM dealership tools to vehicle telematic devices. Hand-held scan tools A range of rugged hand-held scan tools is available.