Cruise Control/Brake Switch A Circuit High
The P0573 code indicates that the powertrain control module (PCM) has detected a high voltage signal from the brake switch A circuit. This typically means the brake switch is stuck closed (always on) or there is a short to voltage in the wiring. The brake switch is a critical safety component that disengages cruise control when the brake pedal is pressed. A high circuit condition can cause the cruise control to not engage or to disengage unexpectedly, and may also affect brake light operation.
1. Most Common Causes
- Faulty brake pedal switch (stuck closed or internal short)
- Signal circuit wire shorted to battery voltage (B+)
- Damaged, corroded, or pushed-out terminals in the switch connector
- Incorrect switch adjustment (contact does not open when pedal is released)
- Internal PCM failure (rare)
2. Symptoms You Will Notice
- Cruise control inoperative or disengages unexpectedly
- Brake lights may stay on constantly
- Check Engine Light illuminated
- Cruise control light flashing or not working
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check freeze frame data.
Step 2: Visually inspect the brake switch and its connector for damage, corrosion, or loose pins.
Step 3: Test the brake switch operation: with the pedal released, the switch should be open (no continuity); with pedal pressed, it should be closed (continuity).
Step 4: Check for voltage at the brake switch connector. With the pedal released, there should be 0V; with pedal pressed, battery voltage. If voltage is present when pedal is released, there is a short to voltage.
Step 5: If switch and wiring are okay, test the PCM input circuit for shorts or opens. Replace the brake switch if faulty.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive, but the brake lights may stay on, which can confuse other drivers and drain the battery. Cruise control will not work. It is recommended to fix it promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts (brake switch) and labor. DIY replacement is inexpensive, around $20-$40 for the switch.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.