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P0593 – Cruise Control Multi-Function Input B Circuit High (OBD2)

P0593 means "Cruise Control Multi-Function Input B Circuit High". The voltage in the cruise control system circuit is above the permitted maximum. For most sensors this points to an open signal or ground wire – the signal "floats" up to the reference voltage – or to a short to voltage.

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P0593 quick summary

Fault codeP0593
MeaningCruise Control Multi-Function Input B Circuit High
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityLow
Can I drive?Yes. Only cruise control is affected; the car drives normally.
Repair cost€10 – €400

How cruise control is monitored

Cruise control holds a set speed using signals from the steering column switches, brake and clutch switches and the vehicle speed; these codes cover the switch inputs and, on older systems, the servo and vacuum control.

Modern cruise control is part of the engine control unit: the multi-function switch on the steering column sends on, off, set, resume, accelerate and coast requests, and the electronic throttle holds the speed. Older systems used a separate servo with vacuum and vent valves or a cable actuator.

Codes in this group report faults in the individual switch signals, stuck buttons, implausible combinations (A/B correlation), the servo and its vacuum/vent control, and a vehicle speed that is too high for cruise control.

Cruise control faults do not affect how the engine runs, but the system is disabled. Common causes are worn steering column switches, a faulty clock spring, brake or clutch switch problems and wiring faults.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 16977 (P0593). Both numbers mean the same fault.

Symptoms of P0593

  • Cruise control does not engage or switches off
  • Buttons do not respond
  • Cruise control indicator flashing
  • Check Engine light on (some vehicles)
  • No effect on normal driving

Most common causes of P0593 (most likely first)

Mechanic's Pro Tip

If cruise control works only intermittently, watch the switch voltage in live data while turning the steering wheel – a failing clock spring shows dropouts at certain angles.

  1. 1.Open circuit in the signal or ground wire

    Most likely

    A loose ground connection is a very common cause.

  2. 2.Signal wire shorted to the 5 V reference or battery voltage

  3. 3.Faulty cruise control system

  4. 4.Brake or clutch switch fault

  5. 5.Wiring or connector fault

  6. 6.Servo or vacuum/vent valve fault (older systems)

Step-by-step diagnostic guide

  1. 1

    Read codes and switch status

    Read the codes and watch each cruise control switch input in live data while pressing the buttons.

  2. 2

    Check signal and ground

    With the ignition on and the cruise control system plugged in, back-probe the signal and ground wires. A signal stuck at reference or battery voltage points to an open ground/signal wire or a short to voltage.

    Multimeter: Ground wire to battery negative: below about 0.1 V. Signal stuck at about 5 V (or 12 V) = open or short to voltage.

  3. 3

    Check brake and clutch switches

    Make sure the brake and clutch switch signals are correct – cruise control will not engage if they report 'pressed'.

  4. 4

    Measure the switch

    Check the switch resistances or voltages per button according to the wiring diagram.

    Multimeter: Many multi-function switches use a resistor ladder: each button gives a different voltage on one signal wire.

  5. 5

    Check the clock spring

    If the switch is on the steering wheel, check the clock spring for open circuits (often other steering wheel functions fail too).

  6. 6

    Replace and verify

    Replace the switch or repair wiring and test cruise control on the road.

Frequently asked questions

Can I keep driving with P0593?

Yes. Only cruise control is affected; the car drives normally.

How much does it cost to fix P0593?

Typical repair costs are 10 € – 400 €, depending on the cause and the vehicle. The most common fixes are: open circuit in the signal or ground wire; signal wire shorted to the 5 V reference or battery voltage; faulty cruise control system. Always confirm the cause with the tests above before buying parts.

Does a cruise control code affect the engine?

No. The engine runs normally; only the cruise function is disabled.

Why does cruise control need the brake switch?

For safety it must disengage when you brake, so a brake switch fault disables it.

What is the difference between P0593 and similar codes?

P0593 belongs to a group of codes for the same component that differ in the type or location of the fault: P0590 – Cruise Control Multi-Function Input B Circuit Stuck; P0591 – Cruise Control Multi-Function Input B Circuit Range/Performance; P0592 – Cruise Control Multi-Function Input B Circuit Low; P0594 – Cruise Control Servo Control Circuit / Open; P0595 – Cruise Control Servo Control Circuit Low; P0596 – Cruise Control Servo Control Circuit High. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.