P2097: Post-catalyst fuel correction reaches the rich limit

P2097 reports excessive rich indication in bank 1 post-catalyst fuel feedback. In the reviewed GM strategy, the controller responds by reducing its integral and proportional offsets, applying a lean bias to fuel control. The fault describes correction authority reaching its lower region, not a direct fuel-pressure measurement.

What counts as a failure

The displayed calibration requires average integral authority at or below minus 90% and average total authority at or below minus 45%. Total authority combines the integral and proportional contributions. These percentages belong to this secondary control strategy; interpreting them as ordinary upstream fuel-trim percentages would change their meaning.

Samples occur every 100 milliseconds, with an average evaluated every 50 seconds. A brief rich transition and a persistent correction-limit problem are therefore different observations.

Interpret purge and operating state

The row refers to P2096 for the operating conditions. That companion description permits cruise and acceleration, while excluding idle and deceleration. Evaluate a completion or recurrence in that context instead of treating any engine-running interval as a valid test.

High vapor loading is another explicit complication. Purge-open vapor of at least 18% for five seconds can suspend the diagnosis; purge closure or vapor at or below 14% for five seconds permits it to resume. A comparison made before and after that change may reflect diagnostic availability.

The source specifies Type B, two-trip behavior. Verification should show that the enabled post-catalyst correction monitor passes after the underlying cause is addressed. The table does not establish a replacement part or prove catalyst damage.

Source and applicability

This explanation is limited to the documented 2025 GM monitor; its thresholds are not universal vehicle specifications. GM diagnostic table, PDF page 592. GM diagnostic table, PDF page 588.