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P0582Cruise Control Vacuum Control Circuit/Open

An open or general fault has been detected in the circuit that drives the cruise control vacuum apply solenoid, so the system cannot build vacuum in the servo and cruise control is disabled.

Definition

On vacuum-operated cruise control systems, the control module energizes a vacuum control solenoid that applies engine or pump vacuum to the servo diaphragm, which pulls the throttle to hold the set speed. The module monitors voltage and current on this driver circuit and sets P0582 when the feedback indicates an open circuit or does not match the commanded state. The typical symptom is cruise control that will not engage or will not hold speed; engine operation and emissions are unaffected. On most applications the MIL does not illuminate, though the cruise indicator lamp may flash or refuse to stay on.

Common causes

  • Open winding in the vacuum control solenoid (usually part of the servo assembly)
  • Broken, chafed, or corroded wiring between the control module and the servo
  • Unplugged, backed-out, or corroded terminal at the servo connector
  • Blown fuse or open power feed to the cruise servo circuit
  • Failed solenoid driver inside the cruise control or engine control module

Common misdiagnoses

  • Complete servo assembly replaced when the fault is a harness or connector problem
  • Brake pedal (stop lamp) switch replaced for a code that is purely a solenoid circuit fault
  • Vehicle speed sensor replaced because cruise is inoperative
  • Steering-wheel cruise switch replaced when the input side is working normally

Troubleshooting steps

  1. 1.Inspect the servo connector

    Unplug the connector at the cruise servo and look for corrosion, spread or backed-out terminals, and chafed wires where the harness routes near the engine.

  2. 2.Measure solenoid resistance

    Measure across the vacuum solenoid terminals at the servo; an OL reading confirms an open winding, and most solenoids spec roughly 20-60 ohms (verify against service data).

  3. 3.Verify the power feed

    With the key on and cruise switched on, confirm battery voltage at the servo feed terminal; if missing, check the cruise fuse and the brake-switch or relay feed path.

  4. 4.Check control-circuit continuity

    With both ends disconnected, verify near-zero ohms from the servo control terminal to the module connector pin, wiggling the harness to expose intermittents.

  5. 5.Command the solenoid with a scan tool

    Use a bidirectional output test to pulse the vacuum solenoid and listen for a click or watch a vacuum gauge teed into the servo line.

  6. 6.Confirm vacuum supply to the servo

    Check the supply hose, check valve, and reservoir for cracks or collapse, since a working solenoid still cannot hold speed without a vacuum source.

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