Mitsubishi Error Code P4: Drain Sensor Error

LED Blink Pattern

How to Fix Mitsubishi Code P4

1. Check for and clear any clogs in the condensate drain line
2. Inspect the drain pan for signs of water buildup
3. If water is present, call a professional HVAC technician

How to Reset Mitsubishi Code P4

1. Turn off the unit using the remote control or wall controller.
2. Turn off the circuit breaker for the outdoor and indoor units. Wait 60 seconds.
3. Restore power at the breaker.
4. Turn the unit on with the remote control. If the error returns, the fault needs professional diagnosis.

Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.

What Does Mitsubishi Error Code P4 Mean?

The P4 error code on your Mitsubishi HVAC system indicates a fault with the drain sensor. This sensor is responsible for detecting water buildup in the condensate pan. When it malfunctions, it can cause your system to shut down to prevent water damage. The most common causes for this error are a clogged drain line or a faulty sensor.

Common Causes

• Clogged condensate drain line
• Faulty drain sensor
• Incorrect sensor installation
• Water pressure issue

Diagnostic Steps

Replacement Parts

Related Codes on Same Models

Other codes that affect the same Mitsubishi model families as P4.