Comprehensive diagnostic guide for OBD-II code P0586

Context and code meaning (based on sources)

• What the code represents: The available open-source definition in Portuguese translates P0586 as which reads as an open circuit in the cruise control vent/solenoid control circuit. In other words, the cruise control system has an open circuit in its control path (likely the solenoid/vent valve circuit used by the cruise control system). This interpretation comes from a GitHub-like open-source code definition. It is important to recognize that manufacturers may use slightly different terminology for related components (solenoid, vacuum vent/valve, actuator, etc.). - Portuguese entry)

• How P0586 fits in OBD-II taxonomy: OBD-II trouble codes are generated by the vehicle's powertrain control module (PCM) to monitor various parameters. They are grouped as powertrain codes that cover emissions-related and engine/ transmission control functions; P0586 falls under the general umbrella of PCM-monitored circuits related to cruise control hardware and its control circuits.

• General diagnostic framework (for context): DTCs are generated by the PCM as it monitors inputs, actuators, and circuits. Troubleshooting typically involves validating the code, reviewing freeze-frame data, inspecting related systems and sensors, and checking electrical, vacuum, and mechanical circuits that could cause an "open circuit" condition.

Symptoms

• Cruise control will not engage or will not maintain set speed.
• Cruise control may intermittently disengage or reset when attempting to engage.
• Cruise control indicator light may illuminate or blink on some vehicles.
• In some cases, related symptoms such as an illuminated MIL or other cruise-control related codes may appear concurrently.

Important Notes

Diagnostic Approach

• Verify the code and gather data: Confirm P0586 with a scan tool, and review freeze-frame data and any concurrent codes. Note vehicle make/model/year and any recent work or conditions (triggering events like electrical work, battery disconnection, or vacuum system changes).
• Check for related codes: Look for other DTCs that point to cruise control inputs (brake switch, clutch switch, accelerator pedal position, vehicle speed sensor) or other PCM faults, as these can affect cruise control behavior and help pinpoint the root cause.
• Plan of attack: Since P0586 points to an open circuit in the cruise control vent/solenoid control path, focus both on electrical wiring/connectors and on the physical cruise control hardware (solenoid/valve and associated vacuum plumbing). Do not overlook related signals that feed the cruise control system (speed sensor, brake switch, etc.), which can cause P0586 to appear in the PCM's logic as a fault condition.

Step-by-Step Diagnosis

1) Confirm and quantify

• Re-scan and confirm P0586, and note any accompanying codes. Record freeze-frame data (engine RPM, vehicle speed, gear, ignition status, etc.) if available.
• Check for activity in the cruise control system via the scan tool's cruise control live data (if supported by the vehicle) to verify whether inputs to the cruise control module are present when attempting to engage.

2) Begin with a visual and harness inspection

• Inspect the cruise control wiring harness, connectors, and the area around the cruise control actuator/solenoid for signs of damage, chafing, corrosion, or loose connections.
• Look for damaged vacuum hoses or pins/terminals associated with the cruise control solenoid/valve. A compromised harness or connector is a common source of "open circuit" conditions.

3) Inspect power, grounds, and fuses

• Verify that the cruise control fuse is intact and that relevant relays (if used by the vehicle's cruise control system) are functioning.
• Check for a good battery voltage supply to the cruise control solenoid/valve circuit and a solid ground path. A floating or high-resistance ground can produce an "open" appearance in certain fault conditions.

4) Inspect brake/clutch and input signals that influence cruise control

• Brake switch (and associated wiring): Test for proper operation and wiring integrity. A faulty brake switch is a common cause of cruise control disengagement and can be associated with diagnostic codes that relate to cruise inputs.
• Clutch switch (for manual-transmission vehicles): Confirm the switch is functioning and wired correctly.
• Vehicle speed sensor (VSS) and accelerator pedal position sensor (APP): Ensure the VSS and APP are providing accurate signals, as improper signals can cause cruise control logic to detect a fault condition.

5) Investigate the cruise control actuator/solenoid and vacuum system

• Locate the cruise control actuator/solenoid and inspect its electrical connector for damage or corrosion.
• Check the resistance of the solenoid coil (if applicable to the vehicle) and verify it is within the manufacturer's specification.
• Inspect the vacuum system: confirm vacuum supply to the actuator, verify vacuum reservoir (if present), and perform a vacuum leak test (smoke test or by applying a hand-held vacuum pump) to detect leaks in hoses, fittings, or the actuator itself.
• If the system uses a vent/solenoid valve, ensure the valve opens and closes as commanded by the PCM and that the vacuum path is unobstructed.

6) Functional/operational testing

• With the ignition on and engine at an appropriate condition (per service information), use a diagnostic tool to command the cruise control on and off. Observe whether the actuator/solenoid responds, and confirm whether the fault symptom changes when the system is commanded.
• If available, perform any vehicle-specific cruise control self-test or actuator test in the scan tool to confirm the circuit's behavior. Note any abnormal readings or lack of response.

7) Correlate findings and determine root cause

• If the harness/connectors show damage, corrosion, or poor continuity, repair wiring and reseat connectors as needed and clear codes. Recheck operation.
• If the solenoid/valve or vacuum lines show leakage or malfunction, repair or replace the faulty components and re-test the system.
• If brake/clutch switch or input sensors are faulty, repair/replace these input devices and re-test.
• If all electrical and vacuum checks pass but P0586 reappears, consider PCM/ECU-related faults or software/calibration issues (verify software status and dealer updates if available). In some cases, a PCM reflash or replacement is necessary, following OEM procedures.

8) Verification and post-repair testing

• Clear codes and perform a drive cycle to verify that the fault does not reoccur. Confirm that cruise control engages, maintains set speed, and disengages only when commanded (brake application, acceleration, or user input) or when the system is turned off.
• Re-scan after testing to ensure no new codes have appeared and that P0586 does not return.

What to replace or repair (prioritization)

• Primary electrical path: any open circuit in the cruise control solenoid/vent valve circuit (harness, connector, or control module pin) identified by resistance tests or continuity checks.
• Vacuum path: replace damaged hoses, fittings, or the actuator/solenoid if vacuum control cannot be verified as functioning.
• Input devices: replace faulty brake/clutch switch, VSS, or APP sensor if their signals are found to be incorrect or intermittent.
• Control unit: if all circuits test good and no mechanical fault is found, consider PCM/ECU software update or replacement as a last resort.

Tools and test equipment you'll commonly need

• OBD-II scan tool capable of reading live data and cruise-control-related parameters (as available for your vehicle)
• Digital multimeter (DVOM) for continuity, resistance, and voltage testing
• Vacuum gauge or hand vacuum pump and smoke machine (for vacuum system testing)
• Basic hand tools (screwdrivers, pliers, torque wrench) for wiring/connector access and component removal
• Vehicle-specific service information for wiring diagrams, resistance specifications, and test procedures (OEM or aftermarket equivalents)

Safety Considerations

• When working with the cruise control vacuum system, avoid sources of high vacuum and ensure the engine is off and cooled when inspecting hoses and the actuator.
• Disconnect the battery or follow proper power-down procedures when performing electrical tests on the air-bag/occupant safety circuits or other sensitive electronics (per shop safety standards and OEM guidelines).
• Be mindful of hot engine surfaces and moving parts during testing, especially when performing functional evaluations.

Summary of causes and relative likelihood (qualitative, field-informed guidance)

• Open circuit in the cruise control solenoid/vent control circuit (highest likelihood for P0586 in many cases): common root cause when the code is present. Approximate expectation in field practice: 40-60%.

• Damaged wiring/ connectors in the cruise control harness or solenoid circuit: plausible cause, particularly after wiring/water exposure or after repairs. Approximate expectation: 20-35%.

• Vacuum system issues (leaks, collapsed hose, failed valve/solenoid): contributes to open-path symptoms and may accompany the code. Approximate expectation: 5-15%.

• Faulty brake/clutch switches or input sensors (which feed cruise control logic): possible and vehicle-dependent. Approximate expectation: 5-15%.

• PCM/ECU software fault or hardware fault: less common but possible, especially if no mechanical/electrical fault is found. Approximate expectation: 5-10%.

• OBD-II - Diagnostic Trouble Codes overview: general description of how DTCs operate within OBD-II and the role of the PCM in monitoring parameters.

• OBD-II - Powertrain Codes: context on powertrain codes within the OBD-II framework.

• OBD-II - Emissions Testing: provides background on the emissions testing landscape relevant to OBD-II diagnostics.

• OBD2 CODE DEFINITIONS . This is the direct code-definition anchor for P0586 from the provided open-source resource. - Portuguese entry)

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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