Brake Switch "A" Circuit Low
The Powertrain Control Module (PCM) detected a low voltage condition in the brake switch 'A' circuit. This typically indicates that the circuit is shorted to ground or the switch has failed, preventing the PCM from accurately determining the brake pedal's position.
This code requires prompt attention because it can prevent the brake lights from illuminating, creating a rear-end collision hazard. It may also prevent the vehicle from shifting out of park.
Common symptoms
- Brake lights remain off when the pedal is pressed
- Brake lights stay on continuously
- Cruise control is disabled or will not engage
- Inability to shift the transmission out of Park
- Check Engine Light (MIL) is illuminated
Likely causes
- Defective or misadjusted brake light switch
- Short to ground in the brake switch 'A' circuit wiring
- Blown brake light fuse (often caused by a short circuit)
- Corroded or loose electrical connector at the brake switch
- Failed brake light bulbs (depending on specific circuit design)
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Check the brake light fuse in the fuse box
Look for: A blown fuse, which indicates a short circuit or overload in the brake light system that must be traced.
Inspect the brake switch and its electrical connector under the dashboard
Look for: Loose connections, melted plastic, backed-out pins, or corrosion at the brake pedal switch connector.
Verify the physical adjustment of the brake switch
Look for: The switch plunger not fully contacting the brake pedal arm when released, or a plunger that is physically stuck.
Test the brake switch for proper continuity using a multimeter
Look for: A reading showing no continuity when the switch is closed, or continuity when it should be open, indicating internal switch failure.
Test the circuit wiring for a short to ground
Look for: Zero or near-zero ohms of resistance between the power supply wire and chassis ground when the switch and module are disconnected.
This page explains the generic P0572 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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