Intermittent system faults in Hyundai iX35?

A poor earth is often the cause of this sort of misbehaviour and it’s a good place to start looking. Check the earthing points in the engine bay and around the area where the tail-lights are earthed in the cargo area.

You might need to lift some carpet or trim pieces, but when you find the earth points, make sure they’re tight and clean and not covered in corrosion. Don’t forget to check the tightness and cleanliness of the battery terminals, too.

Beyond that, these symptoms point to a problem with the car’s body computer which controls all these functions and many more.

When this computer starts to die, all sorts of weird and random flaws can occur. But try this first: Disconnect the battery of the car and let it sit overnight. Reconnect it next morning and keep a close eye on what happens. Sometimes this simple trick will reboot the body computer and normal service will be resumed. Best of all it’s free.