Monitoring Structure

According to the operating principle described above the following main parts of the monitor can be distinguished:

• Monitoring the amount of removed oxygen after fuel cut-off
• Check of monitoring conditions for active test
• Lambda request (interface to lambda control)
• Mixture enrichment in order to remove any stored oxygen
• Measurement of oxygen storage capacity (OSC) by lean A/F ratio operation
• Fault detection

Monitor structure overview: 

Fig 1: OBD Monitor Structure Diagram

Courtesy of BMW OF NORTH AMERICA, INC.