P0573 is a generic OBD-II diagnostic trouble code indicating the Powertrain Control Module detected a high voltage condition in the brake switch “A” signal circuit. This circuit informs the computer when the brake pedal is applied.
This code identifies an electrical circuit condition rather than confirming a single failed component. The underlying cause could involve a misadjusted switch, wiring faults, or a failed brake pedal position sensor, requiring targeted diagnosis.
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Key Takeaways
- P0573 indicates the control module detected an abnormally high voltage or open circuit condition in the brake switch “A” signal circuit.
- Possible causes include a misadjusted or failed brake light switch, damaged wiring, corroded connectors, or a faulty brake pedal position sensor.
- Diagnosis requires verifying brake light operation, inspecting the switch adjustment, and testing the signal circuit voltage and continuity.
- Repairs depend on the confirmed root cause and may involve switch adjustment, wiring repair, or component replacement.
P0573 Code Description and Implications
P0573 indicates that the Powertrain Control Module (PCM) or Engine Control Module (ECM) has detected a high voltage signal on the brake switch “A” circuit.
Modern vehicles use multiple brake switch circuits for redundancy and safety. One circuit typically controls the brake lights, while another sends a signal to the PCM.
The PCM uses this signal to disengage cruise control, release the torque converter clutch, and manage idle air control or electronic throttle responses.
A “circuit high” condition means the PCM is seeing a constant high voltage or an open circuit on this specific signal wire when it expects the voltage to drop as the brake pedal is pressed.
Because P0573 is a generic code, this fundamental electrical monitoring logic applies across various vehicles from multiple manufacturers.
However, the exact switch design, wiring diagrams, and diagnostic troubleshooting steps vary considerably depending on the specific vehicle application.
When diagnosing OBD2 error codes related to brake switch circuits, generic diagnostic paths cannot account for manufacturer-specific pinouts or switch adjustment procedures.
Common Causes of the P0573 Code
The underlying causes for a brake switch circuit high code generally involve the switch itself, its adjustment, or the associated wiring.
Misadjusted Brake Switch: If the brake pedal position sensor or switch is not adjusted correctly, it may not activate when the pedal is pressed, leaving the signal circuit high.
Failed Brake Switch or Sensor: Internal electrical failure within the brake light switch or pedal position sensor can prevent it from completing the circuit and dropping the signal voltage.
Wiring and Connector Issues: An open circuit, broken wire, or corroded connector in the signal path between the brake switch and the PCM will result in a high voltage reading.
Blown Fuses or Power Supply Issues: A lack of reference voltage to the brake switch due to a blown fuse can also cause the module to interpret the signal as an open or high circuit.
Symptoms Associated With P0573
The prominent symptom is the illumination of the Check Engine Light.
Depending on the vehicle’s safety strategies, the cruise control system may become disabled or fail to engage.
Drivers may notice the torque converter clutch failing to unlock, which can cause the engine to stall when coming to a stop.
In some applications, the brake lights may remain illuminated constantly or fail to work entirely.
Shift interlock systems may also be affected, preventing the vehicle from being shifted out of the park position.
Diagnosing the P0573 Trouble Code
Diagnosis must begin by confirming the exact factory service information and wiring diagrams for the vehicle’s make and model.
Start by verifying the operation of the brake lights to determine if the primary brake switch circuit is functioning.
Next, inspect the physical adjustment of the brake switch or pedal position sensor relative to the brake pedal arm.
Use a scan tool capable of displaying live data to monitor the brake switch status while an assistant presses and releases the brake pedal.
If the scan tool does not show a status change, use a digital multimeter to test the switch signal circuit for proper voltage drop and continuity.
Inspect the wiring harness and connectors for physical damage, corrosion, or pushed-out pins.
Repairing the P0573 Issue
Repairs must follow confirmed diagnosis. Never replace the PCM or brake switch solely based on the presence of the code without verifying circuit integrity.
If the brake switch is misadjusted, adjust it to the manufacturer’s exact specification and retest the system.
If external wiring damage or connector corrosion is found, repair the harness and secure the connections before re-evaluating the system.
If electrical testing confirms the brake switch or pedal position sensor has failed internally, replace the component.
Ensure the new switch is properly adjusted and aligned before clearing the codes and verifying the repair.
Cost Considerations for P0573 Repairs
Repair costs vary depending on the confirmed root cause and the specific vehicle application.
Adjusting a misaligned brake switch involves minimal labor and no parts costs.
Replacing a standard brake light switch or pedal position sensor involves basic parts costs and minimal labor.
Repairing damaged wiring in the engine bay or under the dashboard involves standard electrical labor and materials.
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Prevention Strategies for Future Occurrences
Preventing brake switch circuit codes requires attention to the pedal assembly and under-dash environment.
Avoiding excessive force or resting your foot on the brake pedal while driving prevents premature wear and misadjustment of the brake switch plunger.
Inspecting the under-dash wiring harness for interference with the pedal arms can help identify developing chafing or wire damage before it causes an open circuit.
Keeping the pedal assembly clean and free of debris ensures the switch plunger can move freely and return to its resting position.
Troubleshooting Tips and Best Practices
Always check for Technical Service Bulletins related to P0573 for your specific vehicle application.
Manufacturers frequently release updated brake switch designs, revised pedal bump stops, or software updates to address known switch adjustment or circuit faults.
Do not assume the PCM has failed simply because it is the module setting the code.
A simple misadjusted switch, a blown fuse, or a broken wire under the dash are much more probable causes of this specific circuit high code.
If the vehicle recently underwent under-dash work, such as an aftermarket alarm installation or steering column service, verify that no wiring was pinched or connectors left loose.
More OBD-II Codes
| P0551 | P0556 | P0562 | P0563 |
| P0571 | P0572 | P0579 | P0581 |
| P0597 | P0598 | P0599 | P0600 |
| P0504 | P0703 | P0501 | P0500 |
| P0740 | P0741 | P0420 | P0430 |
| P0300 | P0171 | P0174 | P0455 |
Frequently Asked Questions
Is the P0573 code generic or manufacturer-specific?
P0573 is a generic SAE-defined OBD-II code. Its fundamental definition regarding a high voltage condition in the brake switch “A” circuit applies across various manufacturers, though exact diagnostic steps vary.
Can a misadjusted brake switch cause a P0573 code?
Yes. If the brake switch is not adjusted correctly relative to the pedal arm, it may fail to activate when the pedal is pressed. This leaves the signal circuit high, triggering the code.
Will disconnecting the battery clear the P0573 code?
Disconnecting the battery may temporarily clear the code, but it does not repair the underlying electrical or adjustment fault. It also erases valuable freeze frame data and resets readiness monitors.
Can I drive my vehicle with a P0573 code?
Driving is possible but not recommended. A faulty brake switch signal can disable cruise control, prevent the torque converter from unlocking, or interfere with shift interlock and stability control systems.
Does P0573 mean the brake lights will not work?
Not necessarily. Vehicles often use separate circuits or a dual-circuit switch for the brake lights and the PCM signal. The brake lights may function normally even if the PCM signal circuit is open.
What Should You Do About the P0573 Code?
Confirm the exact factory definition and diagnostic procedure for your specific vehicle application before attempting repairs.
Do not assume the Powertrain Control Module has failed based solely on the presence of the diagnostic trouble code.
Inspect the brake switch adjustment, verify the signal circuit continuity, and check for related wiring faults to rule out external issues.
Follow the applicable manufacturer diagnostic workflow to isolate the relevant system and components before replacing any hardware.
