P1586 - Cruise Control Brake Switch 2 Circuit

Introduction:

The diagnostic trouble code (DTC) P1586 indicates a problem within the cruise control system, specifically related to the "Cruise Control Brake Switch 2 Circuit." This fault suggests that the vehicle's computer, often the Powertrain Control Module (PCM), has detected an irregularity in the electrical circuit associated with the secondary brake switch used by the cruise control system. Resolving this issue is crucial for restoring proper cruise control functionality and ensuring safe vehicle operation.

Understanding P1586: A Detailed Guide

Detailed Explanations

Definition of P1586:

The P1586 code signifies that the vehicle's computer has detected an issue with the electrical circuit of the second brake switch, specifically related to the cruise control system. The Powertrain Control Module (PCM) expects a specific signal from this switch when the brake pedal is depressed. This signal is used to disengage the cruise control. A missing, erratic, or inconsistent signal triggers the P1586 DTC.

Function of Brake Switches:

Modern vehicles often employ multiple brake switches for safety and redundancy. Typically, one switch (Brake Switch 1) is primarily responsible for activating the brake lights. The second switch (Brake Switch 2) often serves dedicated functions, such as disengaging the cruise control system, providing input to the ABS (Anti-lock Braking System), or interacting with the transmission control module for shift interlock purposes. The PCM relies on the accurate and consistent signals from these switches to ensure proper vehicle operation and safety.

Symptoms of P1586:

The most common symptom is the malfunctioning of the cruise control system. This can manifest as the inability to engage the cruise control, unexpected disengagement while driving, or failure to disengage when the brake pedal is pressed. The Check Engine Light (MIL) will typically illuminate on the dashboard. Depending on the vehicle and the specific issue, other symptoms may include problems with the ABS system or even transmission shifting issues. It's important to note that brake light functionality may or may not be affected.

Diagnostic Steps:

A systematic approach is crucial for diagnosing P1586. Start with a thorough visual inspection of the brake switch, its wiring, and connectors, looking for any signs of damage, corrosion, or loose connections. Next, verify the brake lights are functioning correctly when the brake pedal is pressed. Use a scan tool to read the DTCs and any freeze frame data associated with the P1586 code. Monitor the brake switch signals in real-time using the scan tool while operating the brake pedal. Use a multimeter to test the continuity and voltage of the brake switch circuit, checking for open circuits, short circuits, and proper voltage levels. Test the brake switch itself using a multimeter to ensure it is functioning correctly. Replace any faulty components, such as the brake switch or damaged wiring. As a last resort, if all other tests fail, suspect a faulty PCM, but this should only be diagnosed by a qualified technician.

Common Mistakes:

One of the most common mistakes is replacing the PCM without properly diagnosing the problem. This is often unnecessary and expensive. Overlooking simple issues like loose connections or corroded terminals is another frequent error. It's also important to test the brake switch itself to ensure it is functioning correctly. Ignoring other related DTCs that may be contributing to the problem can also lead to misdiagnosis. Finally, failing to verify the repair after replacing a component can result in the problem recurring. Make sure you understand the difference between Brake Switch 1 and Brake Switch 2.

Related DTCs:

Several other DTCs can be related to P1586 and can provide valuable clues about the underlying problem. These include P0504 (Brake Switch A/B Correlation), C0051 (Brake Switch Circuit Failure), P0571 (Cruise Control/Brake Switch A Circuit Malfunction), P1585 (Cruise Control Disabled Input), and P1587 (Cruise Control Inhibit Request Circuit). Diagnosing these codes in conjunction with P1586 can help pinpoint the root cause of the issue.

Frequently Asked Questions

• What does the P1586 code mean? The P1586 code indicates a malfunction in the Cruise Control Brake Switch 2 Circuit, meaning the vehicle's computer has detected an issue with the second brake switch circuit used by the cruise control system.

• Will the P1586 code prevent me from driving? The P1586 code usually doesn't prevent driving, but the cruise control system will likely not function correctly. However, it is important to address the issue to ensure safe operation of the vehicle and prevent potential complications.

• Is the P1586 code an easy fix? The difficulty of the fix depends on the underlying cause. Sometimes it's as simple as cleaning a connector or replacing a faulty brake switch. However, more complex issues like wiring problems may require professional diagnosis and repair.

• Can a bad brake switch cause other problems? Yes, a faulty brake switch can affect other systems like the ABS or transmission, especially if the vehicle uses the brake switch signal for multiple functions.

• How do I test the brake switch? You can test the brake switch using a multimeter to check for continuity and proper voltage signals when the switch is activated and deactivated. Refer to your vehicle's repair manual for specific testing procedures.

Conclusion

The P1586 code signifies a problem within the cruise control brake switch 2 circuit, potentially affecting the cruise control system and possibly other vehicle functions. A systematic diagnostic approach, starting with visual inspection and progressing to circuit testing, is essential for accurately identifying and resolving the underlying issue.