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DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P0566

P0566Cruise Control Off Signal

P0566 indicates that the powertrain control module (PCM) has detected a fault in the cruise control system's off signal circuit, meaning the module is not receiving the expected voltage or signal state that confirms the cruise control is switched off. The PCM sets this code when the cruise control off input does not match the commanded state, often due to a wiring issue, a faulty switch, or a communication problem within the cruise control system.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • The cruise control system may not engage or may disengage unexpectedly while driving.
  • The cruise control indicator light on the dashboard may flash or remain illuminated when it should be off.
  • The vehicle may exhibit no noticeable symptoms besides the illuminated check engine light.
  • The horn or other steering wheel-mounted controls may stop working if they share a common circuit.
  • The cruise control may turn off intermittently when driving over bumps or turning the steering wheel.

Common causes, most likely first

  1. Faulty cruise control off switch or button, often due to wear or contamination.
  2. Damaged or corroded wiring in the cruise control off signal circuit, including the clock spring in the steering wheel.
  3. Poor electrical connection at the cruise control module or PCM connectors.
  4. Malfunctioning brake pedal position sensor or clutch pedal position sensor (on manual transmissions) that interferes with the off signal.
  5. Failed cruise control module or PCM, though this is less common.
  6. Aftermarket electronic accessories improperly wired into the cruise control circuit.

How to diagnose and fix it

  1. Inspect the cruise control off switch for physical damage or sticking, and test its continuity with a multimeter.
  2. Check the wiring harness and connectors at the cruise control module, PCM, and steering column for corrosion, loose pins, or chafed wires.
  3. Test the clock spring for continuity, especially if the horn or other steering wheel controls are also malfunctioning.
  4. Verify the brake pedal position sensor operation, as a faulty sensor can send conflicting signals to the cruise control system.
  5. Use a scan tool to monitor the cruise control off signal status in real time while operating the switch to confirm the PCM is receiving the correct input.
  6. If the signal is not reaching the PCM, trace the circuit from the switch to the module and repair any open or short circuits.
  7. If all inputs are correct but the code persists, consult the factory service information for specific pinpoint tests before replacing the cruise control module or PCM.

Cruise Control Off Signal Pitfalls

  • A common oversight is assuming the switch itself is faulty when the real problem is a worn clock spring, which can break the off signal circuit while other steering wheel functions still work.
  • The brake pedal position sensor often shares a signal with the cruise control system, so a misadjusted or failing sensor can set P0566 even though the brake lights appear to work normally.
  • Aftermarket alarms or remote starters tapped into the cruise control wiring can introduce voltage irregularities that mimic a failed off switch, so always check for non-factory wiring.
  • On some vehicles, the cruise control off signal is transmitted over a data bus rather than a dedicated wire, so a communication fault elsewhere can trigger P0566 without any switch problem.
  • The code may be stored as history only if the fault was intermittent, so clearing it and test-driving under various conditions is essential before condemning any parts.

Can I keep driving with P0566?

The vehicle remains safe to drive because the cruise control system is disabled or impaired, but you should avoid using cruise control until the fault is repaired. The check engine light will stay on, and the cruise control may not function, but normal driving is unaffected.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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