P0697: reference circuit 3 faults include rapid variation

P0697 is the ECM's 5-volt reference circuit 3 monitor in the cited table. The generic reference C circuit/open label understates its scope: it checks low level, high level and excessive difference between filtered and instantaneous reference values.

Three ways to fail

The documented level bounds are 88.64 and 93.18 percent of a scale where 100 percent equals 5.5 volts. The difference threshold is 0.90 percentage point. Accordingly, an average that sits inside the level window may still accompany a fault caused by brief variation.

The decision is nineteen of thirty-nine counts or 187.5 milliseconds continuously, with 12.5 milliseconds per count. These short internal checks may capture behavior that a slowly updated scan display does not show clearly; this is an inference from the sample timing, not evidence that a particular external sensor is defective.

Identify circuit 3 before assigning a cause

The row provides no list of devices powered by this reference. Consult the actual controller wiring before linking another sensor's complaint to P0697. Reference circuit numbering cannot safely be inferred from sensor numbering or connector position.

Supply prerequisites also depend on whether the starter is engaged, with separate run/crank voltage conditions. Verification should confirm both a stable reference and a passing monitor in the applicable operating state. The table supports a circuit-integrity interpretation but no universal component-disconnection sequence or controller replacement rule.

Source and applicability

Documented monitors in gm-2025-03a, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 424.