Cruise Control Off Signal
The Powertrain Control Module (PCM) sets this code when it detects an abnormal voltage or lack of response from the cruise control 'Off' switch circuit. This indicates the computer cannot verify the driver's command to turn off or disable the cruise control system via the switch.
This issue is not a safety hazard as the brake pedal will still disengage the cruise control, but the system itself may be disabled until repaired. It is safe to drive the vehicle.
Common symptoms
- Check engine light illuminates
- Cruise control system fails to engage
- Cruise control will not turn off using the steering wheel button
- Cruise control indicator light behaves erratically
- Inability to set a cruising speed
Likely causes
- Faulty cruise control switch
- Damaged or broken clock spring (if switch is steering wheel mounted)
- Corroded or loose wiring connectors in the cruise control circuit
- Blown fuse in the cruise control system
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Connect a scan tool and monitor the cruise control switch data PID.
Look for: Press the 'Off' button and observe if the scan tool registers the state change; if it does not, the switch or circuit is faulty.
Inspect the cruise control switch for physical damage or sticking.
Look for: Look for a button that is physically stuck, broken, or feels unresponsive when pressed.
Test the cruise control switch for continuity using a multimeter.
Look for: Check for proper resistance values when the switch is pressed and released according to the manufacturer's service manual.
Inspect the clock spring and steering column wiring.
Look for: Look for broken wires, poor connections, or high resistance through the clock spring while turning the steering wheel.
Check the wiring harness between the steering column and the PCM.
Look for: Test for continuity, shorts to ground, or shorts to voltage in the signal wire connecting the switch to the engine computer.
This page explains the generic P0566 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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