P0587 Code: Cruise Control Vent Control Circuit Low

What the P0587 code means

The cruise control vent solenoid lets air into the servo so it releases the throttle. For safety, any fault in it disables cruise control.

The computer watches the control circuit from its own driver transistor. The P0587 code means low voltage in the control circuit (a short to ground or a missing power supply). Before you replace the part, check the fuse, relay, connector and wiring, which are the most usual cause.

If the vent does not work, cruise control does not engage or is slow to release the throttle when you brake. For safety, it is best to repair this before you use cruise control again.

To confirm it, unplug the component with the key on and watch what happens to the reading or the code. If the value jumps to the opposite extreme, the wiring is fine and the component is the one pulling the signal to ground. If it does not change, look for the short in the wire, starting where the harness rubs against the engine, the chassis or the exhaust.

P0587 code symptoms

• Check engine light or another warning light on.
• Cruise control that does not work or does not release.
• Cruise control that does not engage.

Likely causes of the P0587 code

1. Control wire shorted to ground. The component may stay on all the time, or the computer cuts the command to protect itself.
2. Interrupted power supply: blown fuse, bad relay or a cut wire.
3. Component with an internal short. Its resistance is far below specification.
4. Connector with moisture. It creates a path to ground.

How to diagnose the P0587 code step by step

1. Activate the component with the scan tool and check whether it responds.
2. Check the fuse and relay. Measure voltage on both sides of the fuse and swap the relay with an identical one.
3. Measure the supply at the connector. You should see battery voltage with the key on or when you command it.
4. Measure the component resistance and compare it with the manual, and also check the insulation to ground.
5. Check the control wire for continuity to the computer and for the absence of shorts.

How to fix the P0587 code

• Repair the connector, the wiring or the power supply.
• Replace the cruise control vent solenoid if it does not respond with correct power and command.
• Clear the codes and verify.

Technical reference data

• 12 V solenoid.
• Reference values only: check the manufacturer data for your vehicle.

Brand-specific notes

This is typical of vacuum cruise control systems.

Frequently asked questions about P0587