Samsung Air Conditioner Error Code U202

The U202 error code on Samsung air conditioners indicates a communication failure between the main MICOM (microcomputer control board) and the sub MICOM in the outdoor unit, or between multiple outdoor units in a multi-unit system. The MICOM boards are responsible for coordinating all operational data across the system, including compressor control, inverter feedback, and sensor readings. When the communication signal between these boards is interrupted or lost entirely, the system registers U202 and halts normal operation to prevent uncontrolled behavior.

The most common technical cause is a loss of the 12V or 5V DC power supply that feeds the sub MICOM or the interconnected outdoor unit. Without stable low-voltage power, the receiving board cannot maintain the communication protocol, and the error is triggered. Wiring faults between the main and sub MICOM boards, including loose connectors, damaged shielding, or corroded terminals, can also disrupt the serial data signal. In multi-outdoor-unit configurations, the interconnect wiring between units is equally susceptible to these failure modes.

Diagnosing U202 begins with performing an error reset using the K3 procedure, then immediately verifying that both 12V and 5V supplies at the affected outdoor unit are within specification. If the voltage rails are stable and the error returns, attention should shift to the physical communication wiring and connector integrity between the main and sub MICOM boards. In persistent cases where wiring checks out, one of the MICOM boards itself may have failed internally.