E231 is a fault on the outdoor condenser coil temperature sensor, which tracks how hot or cold the condenser is running as part of normal system operation. When this sensor develops an open or short circuit, the outdoor board can no longer trust its readings and shuts the system down.
The condenser sensor feeds directly into how the compressor and fan are managed, so an unreliable signal here is treated seriously rather than being allowed to run unchecked. As with most sensor faults, it typically comes down to either a physical connection issue or the sensor itself.
Send us the code and a photo of the display, and a Ford & Doonan technician will get back to you. Please don't reset the unit before you take the photo.
(08) 9331 8800