P057E: erratic brake-position data needs a signal history

P057E detects noisy or erratic brake-pedal position output in the documented GM monitors. Unlike a continuously low or high condition, this failure concerns instability in the input. A single plausible scan reading cannot rule it out.

Same sample rule, different calibration

Both cited tables show five failing samples out of twenty. Their threshold entries differ: 16.00 in 03A and 25.00 in 04B. The displayed rows do not give a physical unit or a complete formula for those thresholds. They are therefore monitor-calibration values, not universal voltage-jump limits for a workshop test.

A useful assessment looks at whether the signal changes smoothly with deliberate pedal movement or becomes erratic while the physical pedal condition is stable. This is an inference from what the monitor detects, not an OEM instruction to condemn a sensor whenever a displayed value moves.

Check for substitution

The published response defaults brake-pedal position to zero percent and sets the code. After that response, a steady zero may hide the unstable input that originally failed. It is important to distinguish a raw channel or recorded signal from a substituted controller position value.

Verification should show that the erratic condition no longer occurs and that the enabled diagnostic passes using the correct vehicle procedure. The tables classify this as a one-trip Type A diagnostic. They do not supply sensor locations, repair likelihoods, or enough information to assess brake-system safety from the code alone.

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 344. GM 2025-04b, page 563.