Outline Of Diagnosis: Notes

This diagnostic monitor performs a functional check of the fuel system to determine an air-fuel ratio cylinder imbalance.

This diagnosis is composed of two monitors.

The outline of "monitor A1" is as follows. When an air-fuel ratio cylinder imbalance occurs, the primary oxygen sensor output signal will oscillate with increased amplitude. This monitor utilizes this behavior to make a diagnosis. The monitor integrates the difference between the amplification value and the mean value of the first oxygen sensor output signal and compares it to a threshold to make a judgment.

The outline of "monitor B1" is as follows. Similarly, when an imbalance occurs, the engine speed also fluctuates with increased amplitude. This monitor utilizes this behavior to make a diagnosis. For reference, it should be noted that this imbalance monitor method is actually similar to the current misfire diagnostic monitor, and the parameter "domg360" (units: degrees CA) is shared between the imbalance and misfire monitors. The imbalance monitor is performed during idle condition when the engine is warm. The monitor integrates the count of "domg360" which exceeds a threshold in 1000 revolution.

When both the "monitor A1" value and the "monitor B1" value exceed a predetermined threshold, this monitor determines a malfunction and stores a fault code.