Fix P0573: Mechanic’s solutions that WORKED

The code P0573 typically indicates an issue with the cruise control brake switch circuit, which can affect the operation of the cruise control system. While not an extremely serious problem, it may lead to inconvenience if your cruise control is not functioning correctly.

P0573 quick overview

Meaning	P0573: Cruise Control Brake Switch Circuit High Voltage
Is it serious?	This code is not extremely serious in terms of safety, but it can affect the functionality of your cruise control system, potentially causing inconvenience during long drives.
Possible causes	– Malfunctioning cruise control brake switch. – Wiring or connector issues in the cruise control brake switch circuit. – Faulty cruise control module. – Issues with the vehicle’s computer or ECM.
How to diagnose?	Inspect for Visible Damage: Examine the brake pedal and position sensor for physical damage. Check Wiring: Inspect wiring for any signs of damage, corrosion, or loose connections. Test Brake Switch Voltage: Measure the voltage output of the brake switch while pressing and releasing the brake pedal. Verify Brake Switch Circuit: Use a multimeter to confirm voltage levels in the brake switch circuit with the ignition on. Look for Short to Voltage: Check for a short to voltage within the brake switch circuit. Inspect Ground Connections: Ensure there are no grounding issues affecting the brake switch circuit. Examine Connector Terminals: Inspect connector terminals for signs of corrosion or poor connections. Monitor Scan Tool Data: Use a scan tool to monitor the brake switch signal while operating the brake pedal. Clear Trouble Codes: After performing tests and any necessary repairs, clear the trouble codes. Test Drive: Confirm that the issue has been resolved and that the code does not reappear during a test drive.
What is Brake Switch?	The brake switch is a component located near the brake pedal in a vehicle. It’s responsible for detecting when the brake pedal is pressed and released and sends signals to various systems, such as the brake lights, cruise control, and engine control module, to initiate appropriate actions.

How to fix P0573 – learn from mechanics

I looked into P0573 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Chevrolet

Vehicle Information:
2007 Chevrolet Uplander LS, 3.9L

Issue + Repair History:

• Warning message displayed: “Service brake system.”
• Two codes were present: P0573 (Brake switch circuit 1 high voltage) and P0703 (Brake switch circuit 2, history code).
• Previous repair included replacing the Brake Pedal Position (BPP) sensor and recalibrating due to these codes.

Suggestions from the Community:

• Ensure the BPP sensor is properly calibrated.
• Check for a short to voltage in the BPP sensor signal circuit.
• Consider replacing the Body Control Module (BCM) if necessary.
• Verify wire connections and correct connector at the BCM.
• Check the voltage on the BPP signal when pressing the pedal; high voltage may indicate high resistance in the low reference circuit or poor terminal fit.
• Investigate a possible bad BCM ground.
• Follow the troubleshooting steps for code P0743, which may hint at a wiring issue.
• Ensure all 3rd brake lights are functioning, as lack of ground feedback to the BCM could be causing the problem.

Final Fix:
The yellow sensor line between the BCM and the brake pedal position sensor was checked and found to have no issues. The problem was traced to a faulty BCM, which was replaced to resolve the issue.

Case #2: Pontiac

Vehicle Information:
2005 Pontiac Grand Prix, 3.8L

Issue + Repair History:

• Cruise control was inoperative.
• Diagnostic Trouble Code (DTC) P0573 (Cruise brake switch circuit current) was present.
• The Body Control Module (BCM) was replaced and reprogrammed according to the Service Information (SI) flow chart, but the issue persisted.
• Tech 2 readings showed discrepancies in applied voltage (9.2V applied, 6.5V released) and the signal side of the brake light switch (5.5V applied, 3.2V released). Tech 2 indicated that the brake was applied at all times.
• All brake and tail light bulbs were functioning correctly, and the vehicle did not have a high-mounted 3rd brake light.

Suggestions from the Community:

• Disconnect the multifunction switch to check if it’s the source of the stray voltage signal.
• Inspect the vehicle for the presence of a high-stop brake lamp, as its absence or malfunction can affect the cruise control.
• Separate the steering column harness at the bottom to identify if the issue is within the column or the multifunction switch.
• Disconnect the brake switch harness to determine if the problem lies within the brake switch.

Final Fix:
A factory-appearing spoiler was found on the deck lid, and under the trunk lid insulation, marks from the nuts holding the factory wing were identified along with a disconnected 2-wire connector. Connecting a test light to this connector restored the system’s functionality. The missing third brake light (CHMSL) was identified as the root cause of the cruise control issue.

Case #3: Volvo

Vehicle Information:
2002 Volvo V70, 2.4L

Issue + Repair History:

• Brake, ABS, traction, and check engine lights were illuminated.
• The brake pedal position sensor was replaced initially, which temporarily resolved the issue, but the lights returned shortly afterward.
• It was suspected that the ABS control module, known for intermittent issues in these cars, could be the cause.

Suggestions from the Community:

• Check for any codes indicating no communication from the ABS module.
• ABS module failures are common in these vehicles.
• Use Volvo diagnostic software (VADIS or VIDA) to retrieve accurate Volvo-specific codes.
• Consider rebuilding or replacing the ABS module if it’s determined to be the cause.

Final Fix:
The issue was likely due to a faulty ABS module, a common problem in these models. The ABS module was replaced or rebuilt to resolve the problem, eliminating the warning lights and restoring proper functionality.