Mitsubishi Air Conditioner Error P4
⚡ Quick Answer: The Mitsubishi Air Conditioner error code P4 indicates a communication failure between the indoor and outdoor units, typically caused by a malfunction... ✅ DIY Fixable
What Does Error P4 Mean?
The Mitsubishi Air Conditioner error code P4 indicates a communication failure between the indoor and outdoor units, typically caused by a malfunctioning drain sensor or wiring issue. This error may lead to the unit ceasing operation to prevent damage, often accompanied by blinking lights or indications of drainage problems. Regular maintenance of the drain system and prompt attention to this error can help ensure optimal performance.
Common Symptoms:
- Error code P4 displayed on remote or unit panel
- Unit may stop operation to protect system
- Possible water drainage issues/overflow indications
Possible Causes
- Drain sensor (float switch/thermistor) malfunction or abnormal reading (medium)
- Poor connection or wiring issue related to the drain sensor (medium)
How to Fix Error P4
DIY Fix Check basic drainage and reset
- Turn off the unit using the remote or main switch
- Inspect visible drain pan and drain hose for blockages or standing water
- After clearing obvious blockages, restore power and attempt restart
Technician Only Inspect and repair drain sensor and related wiring
- Disconnect power to the unit completely
- Access the indoor unit drain area and locate the drain float switch/thermistor
- Check connector seating and wiring integrity to the control board
- Measure sensor resistance against expected normal values
- Replace faulty sensor or repair wiring as needed
- Test operation after repairs
Parts needed: Drain float switch/thermistor, Wiring harness/connectors
- If error persists after basic drainage check and reset
- If you are unfamiliar with safe access to internal components or wiring
- If sensor wiring appears damaged and requires professional diagnosis
Next step
Choose the next step for P4
Confirm the diagnosis before ordering. An error code can identify the system involved, but it does not prove that a specific part has failed.
Most relevant component to inspect
Thermistor
Measures precise temperature changes and sends resistance feedback to the control board.
- Typical part-only price
- $15 - $35
- DIY difficulty
- Easy
- Estimated time
- 15-30 mins
Where can I find the model number?
Check the rating label around the door, lid, frame, rear panel, or inside the appliance cabinet. Use the complete model number, including suffixes.
Verify the complete model and part number on the retailer's compatibility page before ordering.
Other parts options
Check related components first; use model search as a fallback.
Wiring Harness
Connects controls, sensors, motors, and other electrical components inside the appliance.
Model-compatible Air Conditioner parts
Enter the complete model number to browse compatible replacement parts. This is a model-based parts search, not a diagnosis that a specific component failed.
Affiliate disclosure: As an Amazon Associate I earn from qualifying purchases. We may earn a commission from other qualifying purchases or service requests made through links on this page, at no additional cost to you. Recommendations are based on repair relevance, not commission rate.
Optional routine care
Maintenance supplies
These products support cleaning or routine upkeep. They are separate from the possible repair components above and are not claimed to fix this error code or symptom.
Air Conditioner Fin Cleaner
For routine cleaning of accessible coil fins when permitted by the manufacturer. Disconnect power and follow product and appliance instructions.
Model-Compatible Washable AC Filter
A reusable filter option only where the appliance supports one. Match the full model, dimensions, and filter specification.
Compatibility check required: use the complete appliance model and compare the existing filter, bag, or specification before ordering.
Affiliate disclosure: As an Amazon Associate I earn from qualifying purchases. Recommendations are based on routine-care relevance, not commission rate.
Technical Specifications
| wattage | N/A |
|---|---|
| component | Control Board |
| resistance | N/A |
| part_number | Mitsubishi 9320A123 |
| voltage_rating | 220V AC |
Common Questions
What does P4 error mean on Mitsubishi Air Conditioner?
The P4 error indicates a communication failure between indoor and outdoor units, often due to a drain sensor malfunction.
Can I fix Mitsubishi Air Conditioner P4 error myself?
Yes, you can perform basic checks on the drainage system and reset the unit to see if the error resolves.
How much does it cost to fix P4 error?
Repair costs for the P4 error typically range from $50 to $200+, depending on parts and labor in your region.
When should I call a technician for P4?
Call a technician if the error persists after basic checks, if you're unsure about accessing internal components, or if wiring appears damaged.
Sources & References
Data last verified: 2026-07-22
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