The diagnostic trouble code (DTC) P0573 indicates a problem within the cruise control and/or brake switch circuit. This code signifies that the Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected an abnormally high voltage reading from the "A" circuit of the brake switch. This can lead to malfunctioning cruise control and potentially affect braking performance.
This is a serious issue as it affects driver safety. It's crucial to diagnose and repair this fault promptly to restore proper functionality and prevent potential accidents.
| Category | Description | Potential Impact |
|---|---|---|
| Definition | Cruise Control/Brake Switch A Circuit High - The ECM/PCM has detected a voltage reading from the brake switch circuit that is higher than expected. | Cruise control inoperability, potential braking issues, illuminated malfunction indicator lamp (MIL). |
| Possible Causes | Faulty brake light switch, wiring harness issues (shorts to voltage, open circuits), corroded connectors, faulty ECM/PCM (rare). | Cruise control failure, brake light malfunction, ABS/Traction Control system issues. |
| Symptoms | Cruise control not working, brake lights stuck on or not working, ABS light illuminated, traction control light illuminated, engine stalling (rare). | Reduced safety, potential legal issues (brake lights), compromised vehicle control. |
| Diagnosis | Visual inspection of brake light switch and wiring, multimeter testing of voltage and continuity, scan tool data analysis. | Time and effort to diagnose, potential replacement parts cost. |
| Common Solutions | Replacing faulty brake light switch, repairing or replacing damaged wiring, cleaning corroded connectors. | Restoration of cruise control and brake light functionality, improved vehicle safety. |
| Switch Types | Normally Open (NO) - Circuit is open until the brake pedal is pressed. Normally Closed (NC) - Circuit is closed until the brake pedal is pressed. | Understanding the switch type is crucial for accurate testing and diagnosis. |
| Circuit A vs. B | Modern vehicles often have two brake light switches/circuits (A and B) for redundancy and safety features. The specific function of each circuit varies by manufacturer. | Proper identification of the malfunctioning circuit is critical for effective repair. |
| Related Codes | P0571, P0572, P0574, C0051, C0052, C0131, C0161. | Provides a broader understanding of potential issues and helps pinpoint the problem more accurately. |
| ABS/TCS Integration | Brake switch signal is often used by the ABS (Anti-lock Braking System) and TCS (Traction Control System). | Malfunctions can affect ABS and TCS performance, leading to compromised safety. |
| Cruise Control Logic | Cruise control systems use the brake switch signal as a safety mechanism to disengage when the brakes are applied. | A faulty signal prevents cruise control from engaging or disengaging properly. |
| Vehicle Specifics | The exact location and wiring of the brake switch can vary significantly between different makes and models. | Consult a vehicle-specific repair manual or wiring diagram for accurate information. |
| Resistance Testing | Use a multimeter to measure the resistance of the brake switch in both the activated and deactivated states. | Helps determine if the switch is functioning correctly mechanically and electrically. |
| Voltage Testing | Check for proper voltage at the brake switch connector with the ignition on and off. | Verifies that the switch is receiving power and sending the correct signal. |
| Connector Inspection | Carefully inspect the brake switch connector for corrosion, damage, or loose connections. | Ensures a proper electrical connection between the switch and the vehicle's wiring harness. |
| Wiring Diagram | Consult a wiring diagram for the specific vehicle to trace the brake switch circuit and identify potential short circuits or open circuits. | Provides a visual representation of the electrical circuit and helps in troubleshooting. |
| Scan Tool Data | Use a scan tool to monitor the brake switch signal in real-time and identify any inconsistencies or errors. | Allows for dynamic testing and observation of the switch's behavior under different conditions. |
| Brake Light Function | Verify that the brake lights are functioning correctly when the brake pedal is pressed. | Helps determine if the brake switch is properly activating the brake lights. |
| ECU Reset | After repairing the fault, clear the DTCs from the ECU using a scan tool. | Ensures that the ECM/PCM recognizes the repair and resets any related system parameters. |
| Calibration | Some brake switches may require calibration after replacement. Consult the vehicle's service manual for specific instructions. | Ensures that the new switch is properly configured and functioning correctly. |
| Aftermarket Parts | When replacing the brake switch, use a high-quality OEM or reputable aftermarket part. | Avoid using cheap or unreliable parts, as they may fail prematurely or cause other problems. |
| Fuse Inspection | Check the fuse associated with the brake light circuit to ensure it is not blown. | A blown fuse can interrupt the power supply to the brake switch and cause a P0573 code. |
| Ground Connection | Verify that the ground connection for the brake light circuit is secure and free of corrosion. | A poor ground connection can cause voltage drops and affect the operation of the brake switch. |
| Pedal Adjustment | Check the brake pedal travel and adjust the brake switch position if necessary. | Ensures that the switch is activated properly when the brake pedal is pressed. |
| Fluid Level | Inspect the brake fluid level in the master cylinder. | Low brake fluid can sometimes trigger related codes or affect braking performance. |
| Return Spring | Examine the brake pedal return spring to ensure it is functioning correctly. | A weak or broken return spring can prevent the brake pedal from returning to its normal position, potentially affecting the brake switch. |
| Interference | Check for any interference or obstructions that may be affecting the brake pedal or the brake switch. | Obstructions can prevent the brake pedal from being fully depressed or released, potentially affecting the switch's operation. |
Detailed Explanations
Definition: The P0573 code signifies that the vehicle's computer (ECM/PCM) has detected a higher than expected voltage signal coming from circuit "A" of the cruise control/brake switch. This indicates a potential issue with the electrical signal within that specific circuit.
Possible Causes: Several factors can trigger this code. A faulty brake light switch is a common culprit. Damaged wiring, such as a short to voltage, an open circuit, or corroded connectors, can also disrupt the signal. In rare cases, a malfunctioning ECM/PCM could be the cause, but other potential problems should be ruled out first.
Symptoms: The most noticeable symptom is often cruise control not working. Brake lights might be stuck on, not working at all, or intermittent. The ABS and traction control lights might illuminate, indicating problems with those systems. In very rare cases, the engine might stall.
Diagnosis: A thorough diagnosis starts with a visual inspection of the brake light switch and its wiring. A multimeter can be used to test voltage and continuity within the circuit. A scan tool can provide valuable data about the brake switch signal in real-time, aiding in pinpointing the problem.
Common Solutions: Replacing a faulty brake light switch is a frequent solution. Repairing or replacing damaged wiring, and cleaning corroded connectors are also common fixes. Addressing these issues can restore proper circuit function and resolve the code.
Switch Types: Brake light switches are generally either Normally Open (NO) or Normally Closed (NC). A NO switch completes the circuit when the brake pedal is pressed, activating the brake lights. An NC switch breaks the circuit when the brake pedal is pressed. Understanding the switch type is crucial for testing.
Circuit A vs. B: Many modern vehicles use two brake light switches/circuits (A and B) for redundancy. Each circuit might control different functions or systems. The specific roles of circuits A and B vary depending on the vehicle manufacturer and model. Identifying which circuit is malfunctioning is key to efficient repair.
Related Codes: Codes like P0571, P0572, P0574 (related to cruise control and brake switch issues) and C0051, C0052, C0131, C0161 (related to ABS and traction control) can provide a broader picture of the problem. These related codes can help narrow down the potential causes.
ABS/TCS Integration: The brake switch signal is often a critical input for the Anti-lock Braking System (ABS) and Traction Control System (TCS). These systems rely on the brake switch signal to function correctly.
Cruise Control Logic: The cruise control system uses the brake switch signal as a primary safety mechanism. When the brakes are applied, the cruise control is automatically disengaged.
Vehicle Specifics: The location and wiring of the brake light switch differ significantly between vehicle makes and models. Always consult a vehicle-specific repair manual or wiring diagram before attempting any repairs.
Resistance Testing: Use a multimeter to measure the resistance across the brake switch terminals in both the activated (brake pedal pressed) and deactivated (brake pedal released) states. This helps determine if the switch is making proper electrical contact.
Voltage Testing: Check for proper voltage at the brake switch connector with the ignition both on and off. This verifies that the switch is receiving the necessary power and that the signal is being transmitted correctly.
Connector Inspection: Thoroughly inspect the brake switch connector for any signs of corrosion, damage, or loose connections. A poor connection can cause intermittent problems and trigger the P0573 code.
Wiring Diagram: Refer to a wiring diagram specific to your vehicle model to trace the brake switch circuit. This diagram will help you identify potential short circuits, open circuits, or wiring damage.
Scan Tool Data: Use a scan tool that can display live data to monitor the brake switch signal in real-time. This allows you to see how the signal changes when the brake pedal is pressed and released.
Brake Light Function: Visually verify that all brake lights are functioning correctly when the brake pedal is pressed. If some or all of the brake lights are not working, it indicates a problem with the brake switch or the brake light circuit.
ECU Reset: After completing the repairs, clear the DTCs from the Engine Control Unit (ECU) using a scan tool. This will reset the system and allow you to verify that the problem has been resolved.
Calibration: Some brake switches may require calibration after replacement. Consult the vehicle's service manual for specific instructions on how to calibrate the brake switch.
Aftermarket Parts: When replacing the brake switch, use a high-quality OEM (Original Equipment Manufacturer) or reputable aftermarket part. Avoid using cheap or unreliable parts, as they may fail prematurely or cause other problems.
Fuse Inspection: Check the fuse associated with the brake light circuit to ensure it is not blown. A blown fuse can interrupt the power supply to the brake switch and cause a P0573 code.
Ground Connection: Verify that the ground connection for the brake light circuit is secure and free of corrosion. A poor ground connection can cause voltage drops and affect the operation of the brake switch.
Pedal Adjustment: Check the brake pedal travel and adjust the brake switch position if necessary. This ensures that the switch is activated properly when the brake pedal is pressed.
Fluid Level: Inspect the brake fluid level in the master cylinder. Low brake fluid can sometimes trigger related codes or affect braking performance.
Return Spring: Examine the brake pedal return spring to ensure it is functioning correctly. A weak or broken return spring can prevent the brake pedal from returning to its normal position, potentially affecting the brake switch.
Interference: Check for any interference or obstructions that may be affecting the brake pedal or the brake switch. Obstructions can prevent the brake pedal from being fully depressed or released, potentially affecting the switch's operation.
Frequently Asked Questions
What does the P0573 code mean? It means the vehicle's computer has detected an abnormally high voltage signal from the "A" circuit of the cruise control/brake switch. This suggests a problem within that electrical circuit.
What are the common symptoms of a P0573 code? Common symptoms include cruise control not working, brake lights stuck on or not working, and the ABS or traction control lights illuminating.
Can a bad brake light switch cause a P0573 code? Yes, a faulty brake light switch is a very common cause of the P0573 code.
Is it safe to drive with a P0573 code? Driving with a P0573 code can be unsafe, as it can affect your brake lights and cruise control functionality. Addressing the issue is highly recommended.
How do I fix a P0573 code? The fix often involves replacing the brake light switch, repairing damaged wiring, or cleaning corroded connectors. Diagnosis and repair may require professional assistance.
Conclusion
The P0573 diagnostic trouble code indicates a potentially serious issue with the cruise control/brake switch circuit. Thorough diagnosis and prompt repair are essential to restore proper functionality, ensure safety, and prevent further complications. Consulting a qualified mechanic is recommended if you are not comfortable performing electrical troubleshooting and repairs yourself.