P0595 Cruise control: signal or voltage too low (servo)

By: Diagno editorial team · Updated: 2026-10-15

P0595 means: Cruise control: signal or voltage too low (servo). There is a fault in the cruise control or its switches. OK to drive, but have it checked soon. The repair usually costs about €40–250 in Estonia. The most common cause: connector loose, damp or corroded.

What it means

There is a fault in the cruise control or its switches. It doesn't harm the engine, but cruise control may not work. The signal voltage is too low. Usually a wire is broken, a connector is loose or a wire is shorted to ground.

What you may notice

• Cruise control won't engage or drops out
• Engine light may be on

What could be wrong

1. 1Connector loose, damp or corroded
2. 2Wire broken or shorted to ground
3. 3Faulty switch
4. 4Engine computer fault (rare)

Repair difficulty: Easy

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? Check that the brake lights work properly. A faulty brake light switch often switches cruise control off. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the switch

Standard SAE description: Cruise Control Servo Control Circuit Low