I have this code and P0584 together. Does that mean two faults?

Almost certainly the opposite — it means one fault, upstream of both. The two solenoids on a vacuum cruise servo are usually fed from a single supply wire that splices near the top of the engine bay loom and branches to each coil, so a break in that feed makes both channels report high simultaneously. Chasing them as separate problems means testing two healthy solenoids. Start at the supply: check for voltage at both coils with the ignition on, and if neither has it, you have found the job.

Why does nothing look wrong at the servo?

Because the vent is meant to be open when it has no power. That is the deliberate fail-safe that releases the throttle if the system loses supply, and it means a vent circuit that can never be energised leaves the vent sitting exactly where a healthy resting vent sits. There is nothing stuck to see and nothing to hear. The fault only exists during the moment the module tries to close the vent, so on this circuit looking at the part is not a test — you have to command the output and watch the line respond.

The wire beeps for continuity. Can it still be the cause?

Yes, and this is the common trap on the circuit. A meter in continuity mode is looking for any path at all, while the coil needs a path good enough to carry its working current. A terminal that has spread inside its connector, or a joint furred with corrosion, will pass the beep test and still fail once the solenoid tries to draw. Back the terminal out and inspect it under light rather than trusting the tone, and check retention by feel — that is where a real share of these codes hide.

How do I know the repair worked without a long test drive?

Command the vent solenoid on and watch the control line drop toward ground. Because the resting state of this circuit looks correct either way, clearing the code and driving proves little, and the code itself may take a full drive cycle plus an actual cruise engagement before it returns to tell you the truth. A bidirectional output test — or a brief temporary ground on the coil's control terminal, listening for the click — gives you the answer in seconds instead of days.

OBD-II trouble code

P0588: Cruise Control Vent Control Circuit High

Read this code alongside the others in memory before you touch anything. The two servo solenoids usually share one supply, so a high code on both channels is one feed and a high code on this channel alone is this channel — a decision made for free, before the meter comes out.

Low severityPowertrainCruise ControlDrivable short-term

Quick facts

System: Powertrain
Category: Cruise Control
Severity: Low severity
Drivable: Usually safe to drive short-term
Repair cost range: $80 – $600
DIY difficulty: Intermediate DIY

What does P0588 mean?

P0588 means the module found the vent solenoid's control line sitting at a higher voltage than expected. On a circuit the module switches on its ground side, high is what you get when current cannot flow — an open somewhere between the module's output stage and the coil's return, or a coil that has gone open internally, or a supply that never arrives to be switched.

The most useful thing about this code is not in the code itself, it is in what sits beside it in memory. A vacuum cruise servo carries two solenoids, and on most installations they are fed from one supply wire that splices near the top of the engine bay loom and branches to both coils. That shared feed is a single point of failure with a very distinctive signature: when it fails, both channels report high at the same time. So P0588 stored on its own and P0588 stored alongside P0584 are two different jobs. The first is a fault in this channel — its conductor, its connector, its coil, its driver. The second is one fault upstream of both, and testing the vent solenoid in that case is time spent on a healthy part. Reading the whole fault memory before picking up a meter is the cheapest decision available on this code, and it is worth making deliberately rather than by accident.

The second thing worth understanding is why this fault is so quiet. The vent is designed to be open when it is not energised — that is the fail-safe that ensures a loss of power releases the throttle. A vent channel that can never be energised therefore leaves the vent in exactly the position a healthy resting vent occupies. Nothing looks wrong. Nothing sounds wrong. There is no stuck linkage to see, no hiss to hear, no hot component to feel. The fault only exists while the module is trying to close the vent, and at every other moment the hardware presents as normal.

That has a practical consequence that catches people out: on this circuit, observation is not a test. You cannot confirm or eliminate this fault by looking at the servo, and clearing the code and driving away proves very little because the code may need a full drive cycle and an actual cruise engagement before it returns. The efficient path is to command the output — with a scan tool's bidirectional control if you have it, or by grounding the coil's control terminal briefly if you do not — and watch whether the line pulls down. That converts a fault that hides at rest into one that answers immediately.

The third thing is a trap specific to open-circuit faults on low-current control lines. This coil draws a modest current, and a terminal that has spread or backed out inside its connector will pass a continuity test happily while failing under even that small load. A meter set to beep is looking for any path at all; the circuit needs a path good enough to energise a coil. Those are not the same standard, and a connector inspected by eye and by finger pressure will find faults a continuity check clears. On a circuit that lives in the engine bay behind a bulkhead, that is where a meaningful share of these codes actually live.

As for driving, there is nothing to weigh up. Cruise control will not engage, because a module that cannot modulate the vent cannot hold a speed and declines to try. Nothing else about how the car runs changes, no emissions system is involved and no safety function depends on this solenoid. It is a convenience feature that has stopped working, and the only cost of leaving it is that the light stays on and will mask anything else that appears later.

Common causes

Open in the shared supply feed to both servo solenoids, setting this code and P0584 together
Failed splice where the servo supply branches to the two coils near the top of the loom
Open winding inside the vent solenoid
Spread or backed-out terminal on the vent control pin passing continuity but failing under load
Broken conductor in the vent control wire where it crosses the bulkhead
Corroded servo connector with resistance high enough to read as an open under load
Failed module low-side driver for the vent output stuck in the non-conducting state
Connector left unmated or with a broken locking tab after unrelated engine bay work

Symptoms

Cruise control will not engage at all
No click from the servo when cruise control is set
Servo appearing completely normal at rest with nothing visibly or audibly wrong
Both cruise control high codes appearing together after work in the engine bay
Check engine light with the engine running entirely normally
Code returning only after a drive long enough to attempt cruise engagement
Cruise control lamp illuminating and then going out without the system taking control
Fault surviving a repair that fixed a different cruise control complaint

Diagnostic steps

1.Read the whole fault memory first and look specifically for P0584, the matching high code on the vacuum channel. This single observation splits the job in half and costs nothing. Both high together points at something common to the two solenoids — almost always the shared supply feed or the splice that distributes it. This code alone points at the vent channel's own conductor, connector or driver. Do not start testing until you know which of those two you are in.
2.Do not expect to see or hear anything wrong at rest. The vent sits open when de-energised, which is its designed resting state, so a vent circuit that can never be energised looks and behaves exactly like a healthy one until something asks it to close. This is unusual — most faults announce themselves the moment you look at the part — and it means observation is not a test here. You have to command the output.
3.Command the vent solenoid with a scan tool's bidirectional output test and watch the line voltage while it runs. A healthy channel drops sharply toward ground when commanded on. A channel that stays high through the command has an open somewhere between the module's output stage and the coil's return path, and you have just confirmed the code rather than merely read it. If your tool cannot actuate this output, apply a temporary ground to the coil's control terminal instead and listen for the click.
4.If both high codes are stored, find the supply feed's distribution point rather than testing each solenoid. On these installations the two coils are commonly fed from one wire that splices near the top of the loom, which is the hottest and most heat-cycled part of the run. Check for supply voltage at both coils with the ignition on. No supply at either confirms the feed; supply at one and not the other puts the break between the splice and the coil that lost it.
5.Where only this code is stored, work the vent channel's own connector before its wire. Back out the terminal for the vent control pin and look at it under light: a spread or backed-out female terminal makes an intermittent high-resistance joint that reads as an open when the coil tries to draw current but passes a continuity beep perfectly. A continuity test alone will clear this fault, which is the trap on this circuit.
6.Measure the vent coil end to end and compare it against the vacuum coil on the same servo. Two similar readings mean the part is probably sound and the fault is in the vent circuit's wiring; an infinite reading on the vent coil beside a healthy vacuum coil means the winding is open and no amount of harness work will help. Note that this comparison only settles the coil — it says nothing about the supply feed, which is why the code-pairing check in step one comes first.
7.Verify with an actuation test rather than a road test. Because the resting state looks correct, clearing the code and driving away tells you very little on this circuit; the code may take a full drive cycle and a cruise engagement to return. Commanding the vent on and confirming the line pulls down is a faster and more definite proof that the repair took.

Repair cost

$80 – $600

Diagnosis is $80 to $170, and drops toward the low end when the fault memory already tells you whether this is a shared-feed problem or a single-channel one. Repairing the shared supply feed or a failed splice is $70 to $200 with almost no parts cost, and fixes both codes at once. Reterminating or replacing a connector is $60 to $180. A separately available vent solenoid is $30 to $150 plus half an hour to an hour of labour. Where the solenoid is integral to the servo, a complete assembly is $120 to $600 plus one to three hours including linkage adjustment. Used and remanufactured servos are plentiful for the vehicle generations this hardware appears on.

Estimate your repair

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Open the Repair Cost Estimator with cruise control servo / actuator replacement preselected. Adjust labor rate and vehicle category to fit your situation.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.