P2189: Bank 2 lean-at-idle monitoring needs the correct additive trim channel

P2189 concerns the lean-at-idle system condition on bank 2. GM's cited monitor compares that bank's additive long-term fuel-trim component with a positive boundary. A fuel-trim reading from bank 1 or a different correction component cannot stand in for the value named by this code.

The threshold applies after adaptation becomes eligible

The failure limit is additive bank 2 trim above 5.48 percent. Additive adaptation must be active, and the row includes stable multiplicative-adaptation conditions. The continuation requires more than ten seconds of stability, while the threshold evaluation itself is listed as 0.2 second with two-trip reporting.

This means a brief correction after an operating change is not equivalent to an eligible learned-trim result. Preserve adaptation state and the bank-specific parameter definition, not merely the largest percentage visible on the scan display.

Do not silently rewrite the cross-bank term

Within the bank 2 enable continuation, one additive-stability term refers to bank 1. The document does not establish whether that is an intentional cross-bank dependency or inconsistent labeling. This article retains that uncertainty instead of changing every reference to bank 2.

The supported finding is excessive positive additive correction on the named bank. It does not locate an intake leak, injector problem or measurement fault. The exact calibration and diagnostic procedure must resolve the enable interpretation and connect the learned result to a physical cause.

Source and applicability

2025 GM 07A-1 documented monitor only. Vehicle, engine and controller calibration applicability must be established separately; no model fitment is inferred from the file. GM PDF, physical page 263; GM PDF, physical page 264.