Cause
Faulty brake pedal position sensor
The sensor reporting how far the brake pedal has travelled, as distinct from the switch that simply reports whether it is pressed. The distinction is the point of the entry: the switch is a binary contact for the lamps and basic interlocks, while the sensor gives a proportional value that regenerative braking, stability control and adaptive cruise all depend on.
On a hybrid or electric vehicle it is doing real work. The module blends regenerative and friction braking according to pedal travel, so a faulty sensor means it cannot judge how much braking was asked for. The response is to fall back on friction braking alone, which is safe and noticeably different to drive — a heavier pedal and no regeneration.
Modules cross-check the sensor against the switch, so a correlation code between them is common and means the two disagree rather than that either is definitely wrong. A misadjusted switch produces that code with a healthy sensor, which is worth eliminating first since it is an adjustment rather than a part. Watch both through a slow pedal application — the switch should change state early in the travel and the sensor should rise smoothly with it.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (3)
Codes where this is a likely explanation first, rather than merely a possible one.
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