Carrier Hvac Error Code 16

System communication fault — system communications have not been successful for a period exceeding two minutes.

First step from the service manual

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

• 25Invalid motor/model selection
• 26Invalid heater size
• 27Invalid outdoor unit size
• 36Heater output not sensed when energized
• 37Heater output sensed on when not energized
• 41Blower motor fault
• 44Motor communication fault
• 45Control board has failed internal start-up tests and must…