Technical Description of OBD-II Trouble Code
Malfunction in the Cruise Control/Brake Switch A Circuit
What does that signify?
This is a generic diagnostic trouble code (DTC) that applies to OBD-II vehicles. It can be found in various vehicle makes such as Chevrolet, GMC, VW, Audi, Dodge, Jeep, Volkswagen, Volvo, Peugeot, Ram, Chrysler, Kia, Mazda, Harley, Cadillac, etc.
The ECM (engine control module) and other modules not only monitor sensors and switches related to the engine’s functionality, but they also ensure the proper operation of creature comforts like cruise control.
While driving, there are many factors that can affect the speed of your vehicle. Some adaptive cruise control (ACC) systems adjust vehicle speeds based on the surroundings, such as passing, slowing for traffic, lane departure, emergency maneuvers, etc.
However, in this case, the fault refers to a malfunction in the cruise control/brake switch “A” circuit. The brake switch plays a crucial role in the operation of the cruise control system. Since depressing the brake pedal is one way to disable or turn off cruise control, it is important to address this issue, especially if you use cruise control regularly. The letter designation “A” may refer to a specific wire, connector, harness, etc. To determine the exact component associated with this code, consult the appropriate manufacturer-specific service manual. If you’re having trouble finding the necessary information, it’s advisable to look for a wiring diagram for the cruise control system, as it can provide valuable details such as location, specifications, wire colors, etc.
The P0571 Cruise Control/Brake Switch A Circuit Malfunction and related codes (P0572 and P0573) are triggered when the ECM detects a malfunction in the cruise control/brake switch “A” circuit.
Example of a brake switch and its location:
What is the severity of this DTC?
Typically, the severity of cruise control system issues is considered low. However, in this case, it can be classified as moderately-severe due to the potential for the fault to cause the brake switch or cruise control to malfunction.
One of the important functions of the brake switch is to activate the rear brake lights, which inform other drivers about your deceleration or braking. Therefore, its proper operation is crucial for overall driver safety.
What are some of the symptoms of the code?
Symptoms associated with the P0571 diagnostic code may include:
What are some of the common causes of the code?
Possible causes for the P0571 cruise control code include:
What are some diagnostic and troubleshooting steps for P0571?
The first step in troubleshooting any malfunction is to consult the Technical Service Bulletins (TSB) for known issues with the specific vehicle.
Advanced diagnostic steps are highly vehicle-specific and may require specialized equipment and knowledge for accurate execution. The following are basic steps, but refer to a repair guide specific to your vehicle’s year, make, model, and powertrain for detailed instructions.
Basic Step #1
In this case, it is advisable to inspect the brake switch under the dash. It is usually mounted on the brake pedal arm. If the switch is not properly mounted or completely broken, it will be evident upon inspection, potentially saving time and shop fees. If this is the case, replacing the cruise control/brake switch with a new one is recommended. Follow the manufacturer’s specific procedures for installing and adjusting the brake switch to avoid damaging the sensor or causing further issues.
Basic Step #2
Verify the circuit involved. Consult a wiring diagram in your service manual to determine the color codes and designation for the cruise control/brake switch A circuit. To rule out the possibility of a fault in the harness, disconnect one end from the brake switch and the other from the ECM. Using a multimeter, perform various tests, including a continuity test. Manufacturer-provided specifications are necessary to compare actual values with desired ones. Generally, you will be checking the resistance of the circuit to identify any opens or high resistance. During this test, inspect the pins in the connectors, switch, and ECM for corrosion or moisture, which can cause intermittent connections. If corrosion is present, use electrical connection cleaner to remove it before reconnecting everything.
Basic Step #3
Examine the ECM (engine control module). Note that in some cases, the BCM (body control module) monitors and adjusts the cruise control system. Determine which module your system uses and visually inspect it for any water intrusion. If anything seems suspicious, bring your vehicle to a reputable shop or dealer.
