Mitsubishi Electric Air Conditioning Fault Code P4
Fault Code P4: Drain Sensor Error
The P4 fault code in Mitsubishi Electric air conditioning systems indicates a drain sensor error. This Page will cover the symptoms, causes, and repair steps for this fault.
Mitsubishi Electric P4 at a glance
| What it means | The sensor that monitors the condensate drain has developed a fault. |
|---|---|
| How serious | Fault – service needed |
| What you can safely check | Look at where the condensate drain pipe exits outside and check it is not visibly squashed, kinked or blocked |
| Who should fix it | A licensed technician. T&K Airpower are authorised Mitsubishi Electric warranty agents in Adelaide, so if your system is still in warranty we can assess the fault and handle the warranty process for you. |
Symptoms of P4 Fault Code
When the P4 fault code is triggered, you may observe the following symptoms:
- Water Leakage: The system might leak water due to improper drainage.
- System Shutdown: The air conditioner may shut down to prevent further damage.
- Error Notification: The P4 fault code will be displayed on the remote controller or indoor unit.
Possible Causes
The P4 fault code can result from several issues:
- Defective Drain Sensor: The drain sensor may be malfunctioning.
- Blockages: Clogs in the drain line or pump can prevent proper drainage.
- Electrical Issues: Problems with the wiring or connections to the drain sensor.
Repair Solutions
To resolve the P4 fault code, take the following steps:
- Inspect the Drain Sensor: Check the drain sensor for any signs of damage or malfunction. Replace if necessary.
- Clear Blockages: Ensure the drain line and pump are free from obstructions. Clean as needed to restore proper drainage.
- Check Electrical Connections: Verify that the wiring and connections to the drain sensor are secure and undamaged.
By addressing these issues, you can fix the P4 fault code and ensure your Mitsubishi Electric air conditioning system drains properly.
Frequently Asked Questions
What does the P4 fault code mean on a Mitsubishi Electric air conditioner?
The P4 fault code in Mitsubishi Electric air conditioning systems indicates a drain sensor error.
What are the symptoms of a P4 fault?
When the P4 fault code is triggered, you may observe the following symptoms:
- Water Leakage: The system might leak water due to improper drainage.
- System Shutdown: The air conditioner may shut down to prevent further damage.
- Error Notification: The P4 fault code will be displayed on the remote controller or indoor unit.
What causes a P4 fault code?
The P4 fault code can result from several issues:
- Defective Drain Sensor: The drain sensor may be malfunctioning.
- Blockages: Clogs in the drain line or pump can prevent proper drainage.
- Electrical Issues: Problems with the wiring or connections to the drain sensor.
Can I fix a P4 fault myself, or do I need a technician?
A P4 fault should be diagnosed and repaired by a licensed air conditioning technician, not as a DIY job, because the checks involve the unit’s electrical and refrigeration components. As authorised Mitsubishi Electric warranty agents in Adelaide, we diagnose the exact cause first, then quote a fixed price before any work starts. If your system is still under manufacturer warranty, we can assess whether the fault qualifies and handle the warranty process directly. Call 08 8296 7888 to book a diagnostic.
Different code or different brand? Try our fault code lookup. It covers more than 1,000 codes across 15 brands sold in Australia, including the full Mitsubishi Electric list, with plain English meanings and what is safe to check yourself.
Written by Oliver Hastings, T&K Airpower. Last updated 14/09/2026.
