Information about IUMPR

California Air Resources Board (CARB) OBDII Legislation require that all manufactors must record and report operational ratios of non-continuous diagnostic monitors, performed by the Engine Control Module (ECM), for MY05 and subsequent model years. These ratios are called IUMPR (=In-Use Monitoring Performance Ratio).The ratio contains a numerator and a denominator for a predefined selection of monitors. (The number of monitors will increase for later model years.) In addition to this there is also a general denominator.

California Air Resources Board (CARB) OBDII Legislation require that all manufactors must record and report operational ratios of non-continuous diagnostic monitors, performed by the Engine Control Module (ECM), for MY05 and subsequent model years. These ratios are called IUMPR (=In-Use Monitoring Performance Ratio).

The ratio contains a numerator and a denominator for a predefined selection of monitors. (The number of monitors will increase for later model years.) In addition to this there is also a general denominator.

The general denominator will increase by one each driving cycle, but only if the engine has been running for at least 10 minutes, including at least 5 minutes above 25 mph and at least 30 seconds continuous on idle. (Other enviromental conditions, such as high altitude, ambient temperature could inhibit the counter from increasing.)

The numerator will increase by one each driving cycle, but only if the diagnostic monitor has been able to evaluate.

The denominator will also increase by one for each driving cycle, like the general denominator, but in addition some monitor specific conditions have to be fulfilled as well.

The IUMPR service should be used by technican if data has been requested from VCNA.

The Engine Control Module (ECM) should not be cleared from DTC’s before IUMPR read out. Information about set DTC’s could be useful when analyzing the collected data.