P257F: Hood-switch input exceeds its configured electrical range

P257F reports a high-voltage or short-to-voltage signature in the hood-switch input in the reviewed GM strategy. A circuit-high diagnosis is distinct from a valid hood-open state; the controller is judging whether the signal lies within accepted electrical bounds.

Avoid mixing switch variants

The documented selection is Global A, with failure above 85.2%. The table also includes Global B, for which the upper boundary is 67.8%. These are diagnostic signal percentages, not a physical measure of how far the hood is raised.

The different limits make configuration identification essential. A generic percentage shown by a scan tool needs the correct scaling and switch-type interpretation before it can be compared with either number.

How the event is qualified

The monitor uses run/crank as an enable in the listed configuration. It counts 80 failing samples out of 100 on a 12.5-millisecond loop. An isolated high reading and a persistently invalid input therefore carry different weight.

Observe the signal alongside actual hood state and use the vehicle-specific circuit information to locate the electrical problem. This monitor does not establish the latch's mechanical condition or identify a particular shorted wire merely from the high direction.

Following repair, confirm valid switch-state reporting and completion of the enabled diagnostic without recurrence. The source gives Type B, two-trip behavior, but no universal pinout, component location or requirement to replace the hood switch.

Source and applicability

Confirm the reporting module, system and calibration before applying these diagnostic limits. GM diagnostic table, PDF page 661.