In-Use Monitor Performance Ratio

Manufacturers are required to implement software algorithms that track in-use performance for each of the following components: NMHC catalyst, NOx catalyst monitor, NOx absorber monitor, PM filter monitor, exhaust gas sensor monitor, EGR/ VVT monitor, boost pressure monitor, and fuel system monitor. The numerator for each component or system tracks the number of times that all conditions necessary for a specific monitor to detect a malfunction have been encountered. The denominator for each component or system tracks the number of times that the vehicle has been operated in the specified conditions.

Ignition Cycle Counter 

Ignition cycle counter will increment after engine start >= 1 second

"Engine start" is defined as the point when the engine reaches a speed 150 rpm below the normal, warmed-up idle speed (as determined in the drive position for vehicles equipped with an automatic transmission).

General Denominator Counter 

General Denominator counter will increment if all the following conditions are met:

• Ambient Temperature >= -7 deg C (20 deg F)
• Barometric pressure >= 752 hPA (8, 000 ft altitude)
• Time since engine start (or propulsion system active for hybrid) => 600 s
• Time with vehicle speed greater or equal to than 40 kph (25 mph) >= 300 s
• Continuous vehicle operation at idle time (i.e., accelerator pedal released with vehicle speed <= 1.6 kph (1 mph)) >= 30 s

The chart below shows which monitors must complete to increment each IUMPR numerator.