P0595 Code: Cruise Control Servo Control Circuit Low

What the P0595 code means

The cruise control servo moves the throttle to hold speed. It can be vacuum operated or electric, and the computer controls it and monitors its circuit.

The computer watches the control circuit from its own driver transistor. The P0595 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 servo fails, cruise control shuts off. Check that the throttle cable is not snagged or out of adjustment.

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.

P0595 code symptoms

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

Likely causes of the P0595 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 P0595 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 P0595 code

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

Technical reference data

• Electric or vacuum servo, depending on the vehicle.
• Reference values only: check the manufacturer data for your vehicle.

Brand-specific notes

This is uncommon on modern vehicles, where the electronic throttle does this job.

Frequently asked questions about P0595