P026D: fuel adjustment exceeds the applicable upper correction threshold

P026D compares the FSA-released fuel correction with an upper threshold in this GM strategy. The threshold depends on the active combustion-mode group and is multiplied by an ambient-air-pressure factor. The code therefore concerns an adjustment result, not a direct measured excess from a particular injector.

Use the active calibration context

A correction that appears large cannot be judged without its combustion-mode group and ambient-pressure weighting. The document references supporting tables rather than giving one universal mm³ failure value. Preserve that context with the released correction and learning status.

The monitor requires correction release and suitable FSA or DFSA learning to be active. It includes system voltage above 11 V, ambient pressure above 70 kPa and an engine-speed window between 1,100 and 1,800 rpm. Its continuation specifies injected quantity above 15 and below 50 mm³, with stability and vehicle-speed requirements.

A practical distinction from the lower monitor

The documented lower-quantity boundary in this upper-correction test is 15 mm³; it should not be copied from the neighboring lower-correction test's 17-mm³ condition. Similar titles do not guarantee identical enable windows.

Failure accumulation is 200 out of 400 samples at 25 milliseconds each, with Type B, two-trip reporting. Verification needs an eligible completed learning evaluation. The result does not establish an injector replacement or justify high-pressure fuel work without the vehicle-specific professional diagnosis.

Source and applicability

GM 04B, PDF page 1128; GM 04B, PDF page 1129. This explanation covers the documented 2025 monitor. Confirm the vehicle's module, engine and calibration before applying these criteria; the document's vehicle list does not establish this code's applicability to every listed model.