Daikin Mini Split P4 Error Code

Updated 2026-08-29 · review status: manual-verified · reviewed by MiniSplitDecoder Editorial Team Last verified: 2026-08-29

Check your model first

The source record does not specify an exact model family.

Match the model on your equipment label to the linked manufacturer documentation. The same code can mean different things across model families.

Quick answer

P4 means the inverter heat-sink (radiation fin) temperature sensor is reading invalid, so the outdoor unit stops to protect the inverter. One safe power-cycle check; sensor replacement is technician work.

Severity: medium · DIY difficulty: easy

Safety

Stop at the single power-cycle check. Do not open panels or test the sensor with a meter - sensor and board diagnosis is technician-only.

What P4 means

P4 means the outdoor unit cannot trust the inverter radiation-fin (heat sink) temperature sensor reading - the sensor is open, shorted, or out of range, so the inverter stops to protect itself.

Causes, ranked

  1. 1. P4 reading out of range (open or short) common pro only

    Check: Requires resistance measurement against the Daikin service-manual table.

    Fix: Technician: test the sensor, replace if open/short or out of spec.

  2. 2. Transient protection event that clears after one reset common DIY

    Check: Power cycle once at the breaker and run the unit through a full cycle.

    Fix: If the code does not return, monitor; if it returns, stop resetting and schedule service.

  3. 3. Loose sensor connector or damaged sensor lead occasional pro only

    Check: Connector inspection is inside the unit chassis.

    Fix: Technician: reseat or repair the sensor connector and lead.

  4. 4. Control board input fault after the sensor checks out rare pro only

    Check: Board-level voltage checks only.

    Fix: Technician: diagnose the PCB sensor input; replace board if faulty.

Related codes

Cross-references for the same fault family, by brand:

Daikin L4 · Daikin L3 · Daikin E5

Commonly searched as: "daikin p4" · "daikin error code p4" · "daikin air conditioner p4"

Sources

Related Mini Split guides

Mini-Split Communication Error: DIY Checks · Mini-Split Flashing Light Decoder: Blink Patterns · How to Reset a Mini-Split After a Power Outage · Mini-Split Sensor Errors: How to Test a Thermistor