On the majority of passenger vehicles, the post-catalytic converter oxygen sensor (Bank X Sensor 2) is used for monitoring cat health, and does not provide feedback to the ECM for making corrections to the fuel injection rate.

Even though the vehicle does not use post-cat fuel trims, the ECM still reports a value for these trims when requested by a scan tool. As a result, on most vehicles if you monitor short or long term fuel trims for any #2 oxygen sensor you will see a "maxed out" value of 99.2% - this is the ECM's way of reporting that the trim is not in use, and can be ignored.

On the latest versions of the app, post-cat fuel trims will be displayed as N/A instead of 99.2%.