P0573 Code: Here's How to Solve It Fast

The P0573 code is a diagnostic trouble code (DTC) that indicates a problem with the cruise control brake switch circuit. Specifically, it means that the powertrain control module (PCM) has detected a high voltage signal in the cruise control brake switch circuit when it should be low. This code is often associated with issues in the brake switch, wiring, or related components that affect the proper functioning of the cruise control system.

P0573 Code Meaning	P0573 Code Common Causes
Cruise Control/Brake Switch A Circuit High	Faulty brake switch
High voltage detected in brake switch circuit	Damaged or corroded wiring
Malfunction in cruise control system	Misadjusted brake switch
PCM detects abnormal resistance in circuit	Blown fuse
Brake switch signal error	Faulty PCM (rare)

Faulty Brake Switch

The most common cause of the P0573 code is a faulty brake switch. This component is responsible for sending a signal to the PCM when the brake pedal is pressed, which in turn deactivates the cruise control.

Symptoms:

• Cruise control fails to engage or disengage
• Brake lights may not illuminate
• Erratic cruise control operation

Technical explanation:
The brake switch is a normally closed switch. When the brake pedal is pressed, it should open the circuit, sending a low voltage signal to the PCM. If the switch fails, it may send a constant high voltage signal, triggering the P0573 code.

Step-by-step diagnosis:

1. Locate the brake switch near the brake pedal assembly.
2. Disconnect the electrical connector from the switch.
3. Use a multimeter to check for continuity between the switch terminals.
4. With the brake pedal released, there should be continuity.
5. Press the brake pedal, and the continuity should be lost.
6. If the switch doesn't behave as expected, it needs replacement.

Solution:
Replace the faulty brake switch with a new, compatible unit.

Cost estimate:
$20 to $100 for the part, plus 0.5 to 1 hour of labor if professionally installed.

Warning: Ensure the vehicle is in park and the engine is off before working on the brake switch. Improper installation can lead to brake light and cruise control malfunctions, compromising safety.

Damaged or Corroded Wiring

Wiring issues are another common cause of the P0573 code. Damaged, chafed, or corroded wires can create resistance or shorts in the circuit, leading to incorrect voltage readings.

Symptoms:

• Intermittent cruise control operation
• Multiple electrical issues
• Flickering dashboard lights

Technical explanation:
The brake switch circuit requires proper conductivity to function correctly. Any damage to the wiring can introduce resistance or create short circuits, causing the PCM to read incorrect voltage levels.

Step-by-step diagnosis:

1. Visually inspect the wiring harness from the brake switch to the PCM.
2. Look for signs of wear, chafing, or exposed wires, especially near moving parts.
3. Check connectors for corrosion or loose pins.
4. Use a multimeter to test for continuity and proper resistance in the wiring.
5. Perform a voltage drop test to identify any high-resistance connections.

Solution:
Repair or replace damaged wiring. Clean corroded connections and replace any damaged connectors.

Cost estimate:
$50 to $300, depending on the extent of the damage and whether professional repair is needed.

Warning: Electrical repairs require careful attention to detail. Improper repairs can lead to short circuits or electrical fires. If you're unsure, consult a professional.

Misadjusted Brake Switch

Sometimes, the brake switch may be out of adjustment, causing it to send incorrect signals to the PCM.

Symptoms:

• Cruise control engages or disengages at wrong times
• Brake lights may come on without pressing the pedal

Technical explanation:
The brake switch needs to be precisely positioned to activate at the correct point in the brake pedal's travel. If it's misadjusted, it may send signals too early or too late, confusing the PCM.

Step-by-step diagnosis:

1. Locate the brake switch near the top of the brake pedal.
2. Check if there's any play in the switch's mounting.
3. Observe if the switch plunger makes contact with the brake pedal arm.
4. Verify that the switch activates at the beginning of the pedal's travel.

Solution:
Adjust the brake switch position according to the vehicle's service manual specifications. This usually involves loosening the mounting nuts, adjusting the switch, and retightening.

Cost estimate:
$0 to $100, depending on whether you do it yourself or have a professional adjust it.

Warning: Proper adjustment is crucial for both the cruise control and brake light function. If you're unsure about the correct procedure, consult a professional mechanic.

Blown Fuse

A blown fuse in the brake switch or cruise control circuit can cause the P0573 code to appear.

Symptoms:

• Complete loss of cruise control function
• Multiple electrical systems may be affected

Technical explanation:
Fuses are designed to protect electrical circuits from overcurrent situations. If a fuse blows, it can interrupt the circuit, causing the PCM to detect an abnormal condition.

Step-by-step diagnosis:

1. Locate the fuse box using your vehicle's owner's manual.
2. Identify the fuse(s) related to the brake switch and cruise control.
3. Visually inspect the fuse for signs of failure.
4. Use a multimeter or fuse tester to confirm continuity.

Solution:
Replace the blown fuse with one of the same amperage rating.

Cost estimate:
$1 to $5 for a new fuse.

Warning: Never replace a blown fuse with one of a higher amperage rating. This can lead to electrical fires or damage to vehicle components.

Faulty PCM (Rare)

In rare cases, the P0573 code may be caused by a problem within the PCM itself.

Symptoms:

• Multiple, seemingly unrelated error codes
• Erratic behavior of various vehicle systems

Technical explanation:
The PCM is responsible for interpreting signals from various sensors and switches. If it has an internal fault, it may misinterpret the brake switch signal, leading to the P0573 code.

Step-by-step diagnosis:

1. Scan for additional error codes that might indicate a PCM issue.
2. Check PCM ground connections for corrosion or looseness.
3. Verify PCM power supply voltage is within specifications.
4. Use a professional-grade scan tool to test PCM input and output signals.

Solution:
If a PCM fault is confirmed, it will need to be replaced and programmed by a professional.

Cost estimate:
$500 to $2000, depending on the vehicle make and model.

Warning: PCM replacement should only be done by qualified professionals. Improper installation or programming can render the vehicle inoperable or cause severe damage.

Closing Thoughts

The P0573 code, while often related to cruise control issues, can have implications for overall vehicle safety due to its connection with the brake system. While some causes like fuse replacement or switch adjustment can be DIY-friendly, others may require professional diagnosis and repair. Always prioritize safety and consult a certified mechanic if you're unsure about any step in the diagnostic or repair process.

Remember that proper maintenance of your vehicle's electrical system and regular inspections can help prevent issues like the P0573 code from occurring. Keep an eye out for early warning signs such as erratic cruise control behavior or intermittent brake light issues, as addressing these promptly can save you time and money in the long run.

Frequently Asked Questions About P0573

• Can I still drive my car with a P0573 code?
  While the vehicle may still be drivable, it's not recommended. The code indicates a problem with the brake switch circuit, which could affect crucial safety systems.
• Will the P0573 code clear itself?
  It's unlikely the code will clear on its own. Even if it does, the underlying issue remains and the code will likely return.
• How much does it typically cost to fix a P0573 code?
  Costs can range from $20 for a simple fuse replacement to over $1000 for PCM issues. Most repairs fall in the $100-$300 range for brake switch or wiring repairs.
• Can a P0573 code cause my vehicle to fail an emissions test?
  While P0573 is not directly emissions-related, some states require all OBD-II codes to be cleared before passing an emissions test. Check your local regulations.
• Is it safe to clear the P0573 code without fixing the problem?
  It's not recommended. Clearing the code without addressing the underlying issue may temporarily hide the problem but won't solve it, potentially leading to safety concerns.
• Can a bad battery cause a P0573 code?
  While uncommon, a weak battery can cause various electrical issues, including false OBD-II codes. However, it's more likely that the P0573 code is caused by issues specific to the brake switch circuit.
• How long does it take to diagnose and repair a P0573 code?
  Diagnosis typically takes 1-2 hours. Repair time varies from 30 minutes for a simple brake switch replacement to several hours for complex wiring or PCM issues.
• Can weather conditions trigger a P0573 code?
  Extreme weather conditions, particularly moisture or very cold temperatures, can exacerbate existing wiring or connection issues, potentially triggering the P0573 code. However, weather alone is rarely the root cause.