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U2: Serial Communication Error (Mitsubishi)

Mitsubishi heat pump serial communication between indoor and outdoor units has been lost.

What This Error Code Means

The indoor and outdoor control boards cannot communicate with each other via the serial data line.

Common Causes

  • Wiring between indoor and outdoor units damaged
  • Loose connection at terminal block
  • Control board failure
  • Voltage surge damage
  • Rodent damage to communication wire

Affected Brands

Mitsubishi

How ROMA Heating Fixes This

  • Inspect communication wiring between units
  • Check for loose or corroded connections
  • Measure voltage on communication lines
  • Test each control board independently
  • Replace failed wiring or control boards

Why Trust ROMA Heating

24/7 Emergency

True round-the-clock service including weekends and holidays

Licensed Technicians

TSBC licensed and trained on all major heat pump brands

Fast Diagnosis

We know exactly how to interpret and resolve error codes

Related Services

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