Drain Pump Error

What it means

This code appears on the wired remote of Mitsubishi Electric Mr. Slim ducted, ceiling and cassette units. It means the float switch has detected high water in the drain pan and the level does not drop even though the drain pump is running. The unit stops cooling to prevent water from overflowing into the ceiling, and the pump may keep trying. The same code can mean something else on other brands, and wall-mounted Mitsubishi Electric models show errors as lamp blinks with a different meaning.

Models covered: Mitsubishi Electric ducted, ceiling and cassette units (Mr. Slim) with check codes on the wired remote; wall-mounted Mitsubishi Electric models may show errors as lamp blinks with a different meaning.

Related codes: P4P6

Symptoms4

• Cooling stops and P5 shows on the wired remote.
• Dripping water or damp patches on the ceiling around the unit.
• The pump runs nonstop, or cannot be heard at all.
• A musty smell from the air outlets from standing water in the pan.

Possible causes5

• A blocked drain line or pump inlet from dirt and slime, the most common cause in dusty conditions.
• Wrong drain line slope or too much lift after the pump, letting water run back to the pan.
• A failed drain pump motor or a jammed impeller.
• The float switch stuck in the full position by dirt.
• A fault in the pump drive circuit on the indoor board (less common).

How to diagnose5

1. Turn the unit off, switch it off at the breaker, and put a container under any drip to protect the ceiling and furniture.
2. Check that the drain outlet outside or at the drain point is not blocked or submerged.
3. The technician opens the pan cover and checks the water level, pan cleanliness and pump inlet.
4. The technician test-runs the pump to confirm it actually moves water, then checks the float switch moves freely.
5. If the pump gets no power when called for, the control board and its connectors are checked.

How to fix6

1. Clean the drain line, pan and pump inlet thoroughly.
2. Correct the drain line slope or lift according to the installation instructions.
3. Clean and free the float switch if it is stuck.
4. Replace the drain pump if it has failed.
5. Check or replace the control board if it does not drive the pump.
6. Pour water into the pan after the repair and confirm it drains and the code is gone.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

Cleaning the drain line is the cheapest and most common fix; the cost rises for a new pump, a control board, or repairing water damage.

Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026

Frequently asked questions