Skip to main contentStart diagnosing P4 on your Daikin heat pump
What this code means
Radiation fin thermistor or related abnormality.
First step from the service manual
Replace the outdoor unit PCB (main PCB).
Next steps: diagnose the root cause
1
Verify the error code is active
Power cycle the unit and see if the code returns. If it does, the fault is persistent and requires diagnosis.
2
Get the full diagnostic procedure
Get step-by-step guidance, test values, and wiring diagrams from the OEM service manual.
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What’s available for Daikin heat pump models
Access Daikin heat pump service manuals, wiring schematics, exploded parts views, and error code references on MyPros+.