P2177: When bank 1’s learned off-idle fuel correction exceeds its limit

P2177 is commonly described as system too lean off idle on bank 1. The GM monitor here reaches that diagnosis by examining the multiplicative portion of long-term fuel adaptation in gasoline mode. It evaluates a learned correction, not a direct measurement of a particular failed part.

The factor must be both high and eligible

The stated failure boundary is a bank 1 multiplicative factor above 1.27. The row lists a 0.2-second evaluation period, but its continuation requires active adaptation and a stable integrator or the specified similar operating conditions. The short evaluation time does not mean the entire learning process completes in 0.2 seconds.

The stability logic considers engine speed, load and changes in adaptation. Further readiness conditions include thermal and operating-state requirements. A changing transient fuel-trim display is therefore not automatically equivalent to the stable learned value used by this monitor.

What the result does not identify

A positive learned correction indicates the controller has been compensating in the direction represented by the lean code, but it does not distinguish a fuel-delivery issue from an air or measurement problem. The table supplies no ranked list of failed components.

Preserve the bank 1 multiplicative value separately from short-term and additive corrections, along with adaptation status and load. Confirm whether a scan tool displays a factor or a converted percentage before comparing numbers. A valid recovery assessment needs eligible learning and monitor completion rather than only a cleared adaptation memory.

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 170 · GM PDF, physical page 171 · GM PDF, physical page 172.