Theory Of Operation

WARNING: This page is about a different car, the 2016 Dodge Durango. However, it is still accessible from the selected car via links, so may be relevant.

For an aged Upstream O2 Sensor, the response rate to the air/fuel change is slower than when it was new. The O2 Sensor tends to move less with the same air/fuel changes in a given time frame. Therefore by observing the activity of voltage readings from the Upstream O2 Sensor, the quality of the O2 Sensor can be detected.

The O2 Sensor High Frequency Response monitor is used to diagnose the capability of an Upstream O2 Sensor to measure high frequency response. In other words this monitor will determine when an Upstream O2 Sensor has aged or slowed enough that it is no longer useful for Cylinder Imbalance Detection diagnostic monitor.

The test is first run during normal fuel control (non-intrusive). If it cannot detect that the Upstream O2 Sensors frequency response signal is acceptable in the non-intrusive mode within a defined period of test time, the diagnostic monitor will take over fuel control (intrusive) and force an imbalance. Once again, if the Upstream O2 Sensors signal feedback doesn't exceed an acceptable threshold, the diagnostic will indicate a failure. If the diagnostic monitor passes, in either non-intrusive or intrusive mode, the sensor will be considered passing.