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Why is Fuel Trim N/A or 99.2%?

Fuel trim sensor 2 99.2% not used

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.
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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.


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

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