P0572 — Brake switch - low voltage

Causes

• Weak or discharged battery / poor charging system voltage
• Corroded, damaged or loose connector at brake switch
• Wiring short to ground or high resistance in the switch circuit
• Failed brake pedal position/switch assembly
• Blown fuse or faulty relay supplying the circuit
• Poor ground(s) or body/chassis connection

Symptoms

• Brake lights dim, flicker or do not illuminate reliably
• Cruise control may disable or not engage
• Malfunction indicator lamp, ABS or ESC warning lights may be present
• Start/stop or shift-interlock functions may be inhibited
• Related faults stored in other modules (intermittent electrical faults)
• Possible reduced driveability or limp mode in some vehicles

What to check

• Read and record all stored codes and freeze-frame data with a professional scan tool
• Check battery state-of-charge and charging system voltage (engine running ~13.5–14.5 V)
• Visually inspect the brake switch and connector for corrosion, bent pins, water ingress or damage
• Check fuses and relays that feed the brake switch circuit
• Backprobe the brake switch connector and measure supply and output voltages while operating the pedal
• Check continuity and resistance of wiring between switch and control module; look for shorts to ground

Signal parameters

• Supply voltage to switch: typically battery voltage (approx. 11–15 V with engine off or 13–15 V running)
• Switch output: expected to switch between near-battery voltage and near 0 V (or open circuit) depending on switch design
• Low-voltage condition threshold: condition recorded when measured circuit voltage is significantly below battery/charging voltage (varies by manufacturer, often below ~8–9 V)
• Continuity: closed switch should read near 0 Ω, open switch should be high/OL
• Response time: switch state should change immediately with pedal movement (no prolonged delay)

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