E203 could signal a communication timeout inside the outdoor unit itself, specifically between the main control PCB and the inverter PCB that drives the compressor. Unlike E1-type faults, which relate to the indoor-to-outdoor link, this one is an internal breakdown between the two boards housed together in the outdoor cabinet.
Because these two boards need to constantly exchange data to run the compressor safely, even a brief interruption between them will trigger a shutdown. The cause can range from a simple loose connector to a failed board, so proper diagnosis matters here.
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