P2198: Bank 2 rich-biased oxygen sensing and the lower lambda-offset boundary

P2198 is generically bank 2 sensor 1 biased or stuck rich. The GM monitor evaluates the upstream sensor's lambda offset against a lower calibrated boundary. The observed control quantity is distinct from a simple high-voltage oxygen-sensor test.

The correction and eligibility belong together

The main criterion is a bank 2 offset below −0.07. The table qualifies it with offset-adaptation confirmation and a slow-adaptation branch. A 0.1-second evaluation period appears in the row, but the learning and debounce requirements must already be satisfied.

The continuation requires qualified lambda control and sensor readiness, with conditions that exclude active fuel cutoff and manage the transition afterward. A sensor display during another state may not describe the same diagnostic event.

What the fault supports investigating

The code indicates that the bank 2 control result became implausible in the rich-direction category. It does not, by itself, distinguish the physical mixture from sensor or control causes. The sensor's presence in the generic title is not proof it must be replaced.

Retain the actual offset parameter, adaptation state and relevant operating history. Confirm the scan tool's quantity and scale before treating a voltage or trim percentage as equivalent. Cause isolation and verification need the exact vehicle procedure. Resetting the learned offset can remove the displayed correction temporarily without establishing that the conditions which created it have been resolved.

Source and scope

2025 GM 25OBDG07A Part 2 monitor tables only; model, engine and transmission applicability are not established by the unresolved application-matrix filename join. These are documented monitor criteria, not a universal repair procedure. GM PDF, physical page 403 · GM PDF, physical page 404.