P2098: Post-catalyst lean wording and the bank 2 upstream-sensor offset check

P2098 is generically described as post-catalyst fuel trim too lean on bank 2. The cited GM monitor expresses its decision as an out-of-range low lambda offset for the upstream exhaust-gas sensor. That is a description of the control and adaptation logic, not proof that the catalyst itself is defective.

The offset result needs confirmation context

The main lower boundary is an upstream-sensor lambda offset below −0.03. The row's short evaluation period is qualified by offset-adaptation debounce logic. The continuation contains slow-adaptation conditions and information about faults present or healed in the current and previous driving cycles.

Consequently, the code cannot be reduced to one instantaneous rear-sensor voltage reading. The history and adaptation state contribute to how the controller confirms the fault.

Establish which data the tool is displaying

A lambda offset is not the same quantity as short-term fuel-trim percentage or a sensor's raw voltage. Preserve the actual bank 2 offset and control-status information, and verify the parameter definition before comparing it with the source boundary.

The continuation also requires valid upstream lambda operation and qualifications after fuel cutoff. A normal value during an ineligible state cannot independently demonstrate a pass. This monitor identifies an adaptation inconsistency; it does not isolate a sensor, exhaust leak, fuel component or catalyst as the cause. Vehicle-specific diagnostic information is needed to distinguish those possibilities, rather than replacing the part named most prominently in a generic code description.

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 248 · GM PDF, physical page 249 · GM PDF, physical page 250.