P057B: a brake-position signal can fail while remaining in range

P057B monitors a brake-pedal position signal that appears stuck within its allowed range. The cited GM logic evaluates movement using an exponentially weighted moving average, or EWMA. It is not simply another low- or high-input test.

What permits a result

The documented failure evaluation requires no active P057C or P057D electrical faults. It also requires the selector to have been in Park during the key cycle, a qualifying vehicle speed and low accelerator position. These prerequisites matter: a plausible stationary reading does not show that the movement monitor has passed.

The source distinguishes fast and slow passing tests from the failure decision. Passing uses an EWMA above 0.80 with the corresponding sample and test counts; failure uses an EWMA below 0.40 after the specified completed tests. The failure test runs once per key cycle. This means repeatedly checking a fixed pedal position cannot substitute for observing the qualifying movement history.

Calibration limits

The two examples differ in movement and vehicle-speed entries. The 03A table lists speed at least 5; 04B lists at least 8, without identifying units in the displayed row. Do not translate those entries into a road-test instruction.

The practical distinction is between an electrically invalid signal and an electrically plausible signal that fails to respond as expected. A qualified technician should assess the underlying pedal-position trace and prerequisites using the exact vehicle procedure, then verify completion of this particular monitor.

Source and applicability

Documented monitors in gm-2025-03a, gm-2025-04b, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 341. GM 2025-04b, page 560.