P0572 - Cruise Control/Brake Switch A Circuit Low
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0572 is a diagnostic trouble code (DTC) that indicates the Engine Control Module (ECM) has detected a low voltage signal in the brake switch 'A' circuit, which is used by the cruise control system. The ECM monitors this circuit to ensure the cruise control can be safely deactivated when the brake pedal is depressed. A 'low' condition typically means the signal voltage is stuck below a specific threshold, often indicating a short to ground or a failed switch. This fault will disable the cruise control system as a fail-safe measure and may affect torque management and brake signal transmission over the CAN bus.
Possible Causes
Faulty brake light switch (internal electrical failure)
Wiring issues (short to ground or chafed insulation)
Misadjusted brake light switch at the pedal assembly
Corrosion in connectors or blown fuses in the brake circuit
Internal fault in the ECM or Body Control Module (BCM)
Symptoms
Recommended Solution
- Visually check brake light operation and inspect relevant fuses.
- Inspect the connector at the brake pedal switch for oxidation or backed-out pins.
- Measure voltage at the brake switch: It should typically toggle between 0V and 12V (source voltage) when the pedal is pressed/released.
- Perform a resistance (Ohm) test on the switch itself (disconnected); it should show near 0 Ohms when closed and infinite resistance when open.
- Trace the wiring harness between the switch and ECM/BCM to check for shorts to ground.
- Replace the brake light switch and clear the DTCs.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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