Damaged, chafed or shorted wiring to the vent solenoid or valve (short to earth); Faulty cruise control vent solenoid or valve with an internal short; Corroded, loose or water-damaged connector at the solenoid or control unit; Faulty cruise control servo or actuator assembly containing the vent valve; Fault in the control unit driver circuit for the vent output; Outdated control unit software on certain models (check manufacturer information for the specific vehicle).

P0587

Cruise Control Vent Control Circuit Low.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
5: AreaVehicle speed, idle control and auxiliary inputs
87: FaultThe specific fault in that area

What it means

P0587 is the generic code for a low signal in the cruise control vent control circuit. The engine or powertrain control unit monitors the circuit that drives the vent solenoid or valve used by vacuum-operated cruise control systems to release vacuum. It sets the code when the voltage or current it sees on that circuit is lower than expected for the commanded state. Whether a car has this circuit at all depends on the model and the cruise control design.

Symptoms

Cruise control will not engage or drops out unexpectedly
Cruise control cancels itself when a set speed is held
Cruise control warning light or engine management light on
Brake switch or cruise functions behaving oddly alongside the fault
No other noticeable change in normal driving

Possible causes

Damaged, chafed or shorted wiring to the vent solenoid or valve (short to earth)likely
Faulty cruise control vent solenoid or valve with an internal shortlikely
Corroded, loose or water-damaged connector at the solenoid or control unitpossible
Faulty cruise control servo or actuator assembly containing the vent valvepossible
Fault in the control unit driver circuit for the vent outputrare
Outdated control unit software on certain models (check manufacturer information for the specific vehicle)rare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including whether other cruise or brake switch codes are present
Check the cruise control system layout for the specific model, as vent control circuits vary or may not apply to some designs
Inspect the wiring and connector at the vent solenoid or valve and servo for chafing, melted insulation, corrosion and water ingress
Check the wiring loom along its route for rubbing points, particularly near the bulkhead and engine bay brackets
Measure the solenoid or valve coil resistance and compare it with the manufacturer specification
With the circuit unplugged, test the wiring for a short to earth and for continuity back to the control unit
Check the supply voltage and the control signal at the connector while commanding the system, using the manufacturer's test procedure
Clear the code and road test, then recheck for the fault returning

How to fix

Repair or replace damaged wiring and secure the loom away from rubbing points
Replace the vent solenoid or valve, or the servo assembly if the valve is not supplied separately
Clean, repair or replace corroded or damaged connectors and terminals
Replace the control unit only after wiring and the actuator have been proven good and the driver fault is confirmed
Update the control unit software only if the manufacturer lists an outdated calibration as a known cause for this fault

Can I keep driving?

Low severity

The car is normally safe to drive as only the cruise control function is affected. Book it in for repair at a convenient time and avoid relying on cruise control until it is fixed.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.