P0593 Cruise control switch: signal or voltage too high ("B")

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

P0593 means: Cruise control switch: signal or voltage too high ("B"). There is a fault in the cruise control or its switches. OK to drive, but have it checked soon. The most common repair costs about €45–90 in Estonia, depending on make and model. 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 high. Usually a wire is shorted to power, the ground is broken or the part itself has failed.

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 · Wiring or connector repair €45–90
2. 2Wire shorted to power or ground broken · Wiring or connector repair €45–90
3. 3Faulty switch · Switch replacement €50–100
4. 4Engine computer fault (rare) · Control unit check and software €150–300

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 Multi-Function Input "B" Circuit High