E0: Lost communication between indoor and outdoor units

E0 means the indoor and outdoor units have lost communication. The published note says this is common at start-up. The first check on the sheet is the interconnect: look for miswiring, or a broken or disconnected cable #1, the leftmost of the three (it may be labelled differently). That is a wiring check, not a reason to open the refrigerant circuit. After you look, note the code, switch the unit off at the breaker for a few minutes, then switch it back on. If E0 returns, call support with the code and your model number. If the cable is damaged or you are not sure which conductor is #1, stop and call a licensed technician rather than guessing at the terminals.

What to do

1. 1If this appears at initial startup, check for miswiring, or a broken or disconnected cable #1 (the leftmost of 3; it may be labelled differently).
2. 2Note the code, switch the unit off at the breaker for a few minutes, then switch it back on. If the code returns, call support with the code and your model number.