What does it mean?
P1566 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cruise Control Main Switch Circuit Malfunction .
Symptoms
- Cruise control cannot be switched on at all, or the indicator lamp stays lit with the system off
- System switches itself off while driving without any pedal input
- Steering wheel controls such as the horn or audio buttons also behave erratically when a clockspring is at fault
- Airbag warning lamp may illuminate alongside if the clockspring is damaged
- Check engine light on with the code stored
Likely causes
- Worn or burnt contacts inside the cruise on/off switch
- Damaged clockspring in the steering column when the switch is mounted on the steering wheel
- Corroded or loose connector behind the steering column or in the switch cluster
- Broken or chafed wiring between the switch and the control module
- Resistance ladder switch values drifted out of the expected window, which is common on multiplexed switch packs
- Water ingress into the switch assembly after a windscreen or door seal leak
- Failed switch input circuit inside the control module
How to fix it
- Watch the cruise switch status in live data while operating the switch and see whether the module registers the change
- Remove the switch and measure its contact resistance in each position, comparing with the specified values
- Inspect the connector behind the column for corrosion, moisture and loose terminals
- Check the clockspring for continuity through the full steering wheel travel, turning the wheel slowly lock to lock
- Test the wiring between the switch and the module for continuity and shorts
- Replace the switch or the clockspring when it fails the measurement, following the correct centring procedure
- Clear the code and confirm the system arms and cancels correctly on a road test