P0307: cylinder-7 misfire counts versus an exhaust-bank total

P0307 attributes misfire to cylinder 7, but the cited monitor compares that cylinder with larger engine or exhaust-bank totals. It is therefore useful to preserve the surrounding misfire distribution rather than viewing the cylinder-7 number in isolation.

Two denominators are used

The emissions calculation uses ten percent of total engine misfire counts for the cylinder-specific comparison. The first frame covers 1,000 crankshaft revolutions, and the later emissions path lists four such frames with a total-count threshold above 120.

The catalyst-damage calculation uses twenty percent of the weighted exhaust-bank total instead. It lists a weighted threshold above 3,000 and a 200-revolution frame. “Engine total” and “bank weighted total” are not interchangeable denominators.

Follow the path that actually failed

A broad distribution of ordinary counts and a concentrated weighted contribution can lead to different interpretations of the diagnostic data. Record the path and counter type before making conclusions about whether cylinder 7 is the sole affected cylinder.

The source lists two-trip reporting and requires eligible combustion states and valid timing information. Verification should reproduce the relevant monitoring opportunity through the proper service procedure. This code does not establish the physical position of cylinder 7 in an unidentified engine or directly identify a faulty component.

Documentation and applicability

These details describe the monitor in GM’s 2025 25OBDG07A Part2 file. Its application-matrix filename does not match the download index, so model and engine applicability remain unresolved. Use the vehicle’s correct service information before applying these calibration details.

GM diagnostic table, PDF page 149; GM diagnostic table, PDF page 150; GM diagnostic table, PDF page 151.