51 In-use monitor performance ratio-kernel function: Notes

The in-use monitor performance (IUMPR) kernel function represents the core of the software algorithms in the OBD II system implemented to individually track and report in-use monitor performance, in the standardized tracking and reporting format, for every monitor of the following components/systems (subsystems A...E):

A: catalyst
B: primary oxygen sensor
C: evaporative system (only 0.02 inch leak detection)
D: VVT system and
E: secondary air system (not implemented in this engine).

All monitors for which an in-use performance record is required do have an interface (a function identifier) through which they communicate with the IUMPR kernel function. It is this kernel function that does the actual tracking and preparation for reporting in the standardized format as depicted in Fig 1. The IUMPR kernel function additionally tracks and records the ignition cycle counter, the general denominator for every driving cycle and determines the monitor with the lowest numerical ratio within each group that has multiple monitors.

Fig 1: Schematic View Of In-Use Monitor Performance Ratio Implementation

Courtesy of BMW OF NORTH AMERICA, INC.