Drivers who encounter a constantly illuminated brake‑pedal‑position lamp, an ABS or traction‑control warning that appears at a stop, or a sudden loss of brake‑related safety features are likely seeing the result of a P0573 Brake Switch A Circuit High condition. The fault indicates that the vehicle’s control module is reading a voltage level far above the normal range for the brake‑switch circuit, which it interprets as a “high” condition. Because the brake‑switch signal feeds the anti‑lock braking system (ABS), electronic stability control (ESC), and other safety functions, the fault can disable those systems until the issue is cleared. Early identification of the underlying module or wiring problem is essential to restore full brake‑system functionality and avoid unexpected safety‑system shutdowns.
These symptoms appear immediately after the fault is logged and persist until the circuit condition returns to normal or the module is reprogrammed/replaced.
The brake‑switch is a simple on/off contact that tells the control module when the pedal is depressed. Mechanical wear, corrosion, or a broken contact can cause the switch to stay open, presenting an abnormally high voltage to the module’s input.
A shorted wire (e.g., damaged harness, chafed insulation) can feed the module a constant 12 V or higher, triggering the “high” reading. Conversely, an open circuit combined with a pull‑up resistor can also produce a voltage that the module interprets as high.
Modern vehicles route the brake‑switch signal through the Body Control Module (BCM) or a dedicated Brake Control Module (BCM‑type). Internal component failure—such as a damaged analog‑to‑digital converter, burned‑out driver, or corrupted firmware—can cause the module to misread a normal‑range voltage as high.
A regulator that supplies the brake‑switch circuit with an elevated voltage (e.g., 15 V instead of 12 V) will push the input beyond the module’s threshold, resulting in a P0573 condition. This is often linked to a failing power‑distribution module or a grounding issue that raises the reference voltage.
– Connect a professional OBD‑II scanner capable of manufacturer‑specific data. Record all related codes (P0572, P0574, ABS‑related codes). Clear the codes and note whether P0573 returns after a drive cycle.
– Locate the brake‑switch harness near the pedal assembly. Check for frayed conductors, corrosion, or loose connectors. Follow the wiring to the BCM/Brake Control Module, inspecting the connector pins for bent contacts or moisture.
– With the ignition on and the brake pedal released, measure the voltage at the switch’s “A” terminal using a digital multimeter. A reading near 12 V indicates an open circuit; a reading significantly above 12 V (e.g., >13 V) suggests a short or regulator issue.
– Depress the brake pedal and observe the voltage change. A proper switch should pull the circuit to ground (0 V) when engaged. If the voltage does not change, the switch or wiring is suspect.
– Using the scanner, perform a “module self‑test” or “communication verification” for the BCM/Brake Control Module. A failure indicates internal module corruption or a communication bus fault.
– If wiring is damaged: Repair or replace the harness segment; ensure proper crimping and shielding.
– If the switch is confirmed stuck open: Although the switch itself is a non‑module part, the fault may still be logged in the module. Replace the switch and re‑test the circuit; if the P0573 persists, proceed to module diagnostics.
– Minor firmware glitches can sometimes be cleared by re‑flashing the module. Use the manufacturer’s re‑programming tool to load the latest calibration. If the module fails the self‑test after re‑flash, replacement is advisable.
– Module re‑programming: $120‑$200 for software load plus $50‑$80 labor.
– Module replacement: $600‑$900 for a VIN‑matched unit plus $200‑$300 labor.
– Wiring repair: $50‑$150 for parts and labor, depending on harness length.
All repairs should be verified by clearing the code, performing a road test, and confirming that the BPP lamp and ABS/ESC warnings remain off.
If the Body or Brake Control Module fails its built‑in self‑test after a complete wiring and switch inspection, or if re‑flashing does not eliminate the P0573 code, the module is likely suffering from internal hardware degradation. Continued operation of a compromised module can lead to intermittent loss of safety functions and may trigger additional fault codes, increasing diagnostic time and repair expense.
Modern control modules are deeply integrated with vehicle security, immobilizer, and safety networks. Selecting a replacement is not merely a hardware swap; it requires precise VIN‑matched programming to ensure seamless communication with ABS, ESC, and other safety systems.
Flagship One specializes in VIN‑matched control modules, providing a plug‑and‑drive solution backed by a comprehensive warranty. Their technicians verify software compatibility, perform factory‑level programming, and ship the calibrated unit ready for installation, minimizing downtime and eliminating the risk of mismatched firmware.
Following these steps helps maintain proper signal integrity and reduces the likelihood of a high‑circuit condition that would set P0573.
Service Recommendation: Most issues related to this fault are diagnosed and corrected through inspection, wiring repair, and calibration rather than module replacement. For modules not typically replaced through aftermarket suppliers, diagnosis and repair should be performed by a certified automotive technician with access to factory service information and tooling.