Chat with one of our friendly reps to get help quick.

Something on your mind not found here? E-mail us.

We offer phone support if you don't want to type.

Support Center

<h2 id="isPasted"><u>Introduction</u></h2><p>The &quot;P4&quot; error code indicates the outdoor unit is undergoing discharge temperature overheating protection. This article is for the following systems:</p><ul><li id="isPasted"><a href="https://www.pioneerminisplit.com/collections/quantum-fresh-series-breathe-the-difference" target="_blank" rel="noopener noreferrer">Quantum Fresh High-Wall (WYT-FA)</a></li><li><a href="https://www.pioneerminisplit.com/collections/quantum-hyperformance-high-wall-series" target="_blank" rel="noopener noreferrer">Quantum Hyperformance High-Wall (WYT-25)</a></li><li><a href="https://www.pioneerminisplit.com/collections/quantum-ultra-ceiling-cassette" target="_blank" rel="noopener noreferrer">Quantum Ultra Ceiling Cassette (CYT-24)</a></li><li><a href="https://www.pioneerminisplit.com/collections/quantum-ultra-ducted-ceiling-concealed" target="_blank" rel="noopener noreferrer">Quantum Ultra Ducted Ceiling Concealed (RYT-24)</a></li><li><a href="https://www.pioneerminisplit.com/collections/quantum-ultra-universal-flex-series" target="_blank" rel="noopener noreferrer">Quantum Ultra Floor-Ceiling Flex (UYT-24)</a></li><li><a href="https://www.pioneerminisplit.com/collections/quantum-ultra-high-wall-series" target="_blank" rel="noopener noreferrer">Quantum Ultra High-Wall (WYT-24)</a></li></ul><h2 id="troubleshooting-diagram"><u>Troubleshooting Diagram</u><u><img src="https://attachments.gorgias.help/Q9r0k7BYaV2vg13y/hc/9JWjXVxG8m6DvMqm/2025111414-088ced10-b2cf-421a-a0d5-071481b14978-p4_troubleshooting_diagram.png" style="width: 1000px;" class="fr-fic fr-dib fr-bordered"></u><br></h2>

This error code indicates the outdoor unit is undergoing discharge temperature overheating protection. This troubleshooting article is for Quantum series systems.

P4 Error Code (Quantum Series)

Troubleshooting

By Error Code

Diamante & Quantum Systems

Pioneer Offers Hyper-Heat Units

Pioneer Systems Offer Both Heating & Cooling Functions

Understand the Difference Between 115V & 230V Systems

Understand the Refrigerants Used for Each Model

How to Choose a System

Mini Splits are Capable of Using Fewer Indoor Units than the Outdoor Unit’s Zonal Capacity

Pioneer Mini Splits Function as Dehumidifiers

Pioneer Offers Different Lineset Lengths

Pioneer Offers Pre-Charged Linesets

Pioneer Offers Pre-Flared Linesets

Pioneer Systems Include Factory Pre-Charged Refrigerant

Single-Zone Mini Splits Cannot be Used with Multiple Indoor Units

Understand how Mini Splits are Powered

Understand the Life Expectancy of Pioneer Systems

Understand the Meaning of “Multi-Zone”

Mini-Split Basics

Determine the Unit Size Needed for Your Space

Match the Lineset Diameter to Your Pioneer Indoor Unit

Understand Why Short Cycling Occurs When Sizing Systems

Sizing & Efficiency Guide

Start Here

Understand the Differences Between Inverter+ & Inverter++ Systems

Understand the Differences Between the Wall-Mounted Ductless Mini Splits

Understand Which Units are Rated Energy-Star

Compare Models

Learn About the Discounts Available

Learn About the Energy-Star Tax Credits Available for Pioneer Systems

Learn More about IRA Tax Credits

Learn Why Your Pioneer Discount Code Only Says "SAMPLE"

Redeem Your Pioneer Rewards Points When Shopping Online

Understand How to Manage Multiple Credit Card Charges with Pioneer

Financing & Payment

Learn About Our Shipping & Delivery Details

Understand the Qualifications for Free Shipping

Order Status & Shipping

Diamante Essenza High-Wall (WYT-17) Overview

Diamante Pro High-Wall (WYT-20) Overview

Quantum Fresh High-Wall (WYT-FA) Overview

Quantum Hyperformance High-Wall (WYT-25) Overview

Quantum Ultra Ceiling Cassette (CYT-24) Overview

Quantum Ultra Ducted Ceiling Concealed (RYT-24) Overview

Quantum Ultra Floor-Ceiling Flex (UYT-24) Overview

Quantum Ultra High-Wall (WYT-24) Overview

Quantum Ultra Multi-Zone Overview

Vertex Ducted Central Split (DYC-18) Overview

Ducted & Ductless Systems

ECOasis 50 Ductless Wall-Mounted Single-Room Energy Recovery Ventilator (ERV) Overview

ECOasis 150 Ductless Wall-Mounted Single-Room Energy Recovery Ventilator (ERV) Overview

Energy Recovery Ventilators

QHD070 Whole-House Ducted Dehumidifier (QHD) Overview

High Performance Dehumidifier

Full Inverter Rooftop RV Air Conditioner Heat Pump (PYZ) Overview

Under-Bench RV Inverter Packaged Heat Pump Air Conditioner (PYR) Overview

Recreational Vehicle Systems

Product Line Overviews

Find Out How to Complete Returns

Figure Out How to Start Your Return

Learn About Our Policy for Undeliverable or Refused Shipments

Learn About Our Return Policy

Understand How to Return an Item

Understand the Eligibility Requirements for Refunds

Understand Our Return Fees

Understand Our Return Process

Returns & Refunds

Shopping & Pre-Purchase

Find an Installer for Your System

Find Professionals to Install Your Pioneer System

Learn Who is Permitted to Install Your System

Understand if Our Systems can be Self-Installed

Understand the Cost & Time Spent on Installing Systems

First-Time Setup

Connect the Refrigerant Piping to the Indoor Unit

Cassette Units

Ducted Units

Flex Units

Wall-Mounted Units

Indoor Units

Angle Linesets Upward

Complete the Safety Checks & Test Run

Find Out if a Wall-Mounted Indoor Unit can be Set onto Ceilings

Find Out if the Indoor Unit Requires Anything Extra in Order to be Wall-Mounted

Find Out the Ideal Height for Mounting Indoor Units

Leakage Inspection & Vacuuming for Refrigerant Lines

Learn the Gauge of Wire Used for Ductless System Connections

Open the Service Valve

Set Up the Lineset to Exit from the Side of the Indoor Unit

Understand the 6-Foot Plastic Whips & 4-Lead Mini Split Connection Wire

Understand how to Properly Uncoil the Lineset

Understand the Drilling Details to Accommodate Drain & Refrigerant Lines

Understand the Requirements for Installing Your System

Understand the Torque Wrench Size for Installing Your System

Installation Requirements

Understand the Allowable Zone Combinations for Multi-Zone Systems

Multi-Zone Units

Install Outdoor Units: Getting Started

Air Evacuation & Bleed the Circuit for Outdoor Units

Connect the Electrical Wiring for Outdoor Units

Connect the Refrigerant Piping to the Outdoor Unit

Mount the Outdoor Unit

Select the Installation Location for Outdoor Units

Select the Installation Location for Ducted Central Split Outdoor Units

Set Up the Condensate Water Drainage for Outdoor Units

Understand How to Install Ducted Central Split Outdoor Units on Support Pads

Outdoor Units

Ductless & Ducted Systems

Install ECOasis 50 Energy Recovery Ventilators

Install ECOasis 150 Energy Recover Ventilators

Energy Recovery Ventilator

Connect the Drain Fitting for QHD070 Whole-House Ducted Dehumidifiers

High Performance Dehumidifiers

Install Rooftop RV Systems: Getting Started

Create the Roof Opening for Rooftop RV Systems

Install the Air Duct & Top Mounting Plate for Rooftop RV Systems

Mount the Panel for Rooftop RV Systems

Place the Unit onto the Roof for Rooftop RV Systems

Setup the Electrical Wiring for Rooftop RV Systems

Setup the System Connections for Rooftop RV Systems

Understand the Installation Requirements for Rooftop RV Systems

Rooftop RV Inverter

Install Under-Bench RV Systems: Getting Started

Connect & Power Up Under-Bench RV Systems

Create the Floor Openings for Under-Bench RV Systems

Create the Recirculation Air Opening for Under-Bench RV Systems

Fasten the Under-Bench RV System into Place

Install the Wall Thermostat for Under-Bench RV Systems

Understand the Ductwork Best Practices for Under-Bench RV Systems

Understand the Installation Requirements for Under-Bench RV Systems

Under-Bench RV Inverter

Installation & Setup

Understand the DIP Switches for Vertex Ducted Central Split Systems

DIP Switch Layouts

Turn the LED Display On or Off

Understand the Display Board for Ducted Ceiling Concealed Systems

Understand the Display Panel for Rooftop RV Systems

Understand the Front Panel Displays for Ceiling Cassette Systems

Understand the Front Panel Display for Floor-Ceiling Flex Systems

Understand the Front Panel Display for Wall-Mounted Systems

Understand the Master Unit Display for ECOasis 50 Energy Recovery Ventilators

Understand the Onboard Controller & Terminal Block Layout for QHD070 Whole-House Ducted Dehumidifiers

Understand the Wall Controller Display for RV Under-Bench Systems

Display Layouts

CL Error Code

Clean the Filters for Diamante Essenza & Pro High-Wall Systems

Clean the Filters for Quantum Fresh High-Wall Systems

Clean the Filters for Quantum Ultra Ceiling Cassette Systems

Clean the Filters for Quantum Ultra Ducted Ceiling Concealed Systems

Clean the Filters for Quantum Ultra Floor-Ceiling Flex Systems

Clean the Filters for Quantum Ultra & Hyperformance High-Wall Systems

Clean the Filter Screen for Rooftop RV Systems

Clean the Filters for Under-Bench RV Systems

Filter Cleaning & CL Code

Activate Auto Mode

Activate the Child-Lock Function

Activate Cooling Mode

Activate Dry Mode

Activate Energy Saver (ECO) Mode

Activate Fan-Only Mode

Activate the Fresh Air Feature for Quantum Fresh High-Wall Systems

Activate Gentle Wind Mode for Quantum Fresh High-Wall Systems

Activate Heating Mode

Activate the I Feel Feature

Activate the Memory Feature

Activate Mute Mode

Activate the Self-Clean Feature

Activate Sleep Mode

Activate the Timer On/Timer Off Function

Activate Turbo Mode

Activate 46°F Freeze Protection

Understand the Auto-Restart Feature

Understand the Voice Control Feature For Quantum Fresh High-Wall Systems

Understand the Defrost Function

Understand the Dehumidification Function

Understand the Drainage Functions

QHD070 Whole-House Dehumidifiers

Activate Dehumidification Mode

Activate Night Mode

Activate Ventilation Mode

Rooftop RV Systems

Under-Bench RV Systems

Activate the Accelerated Cooling/Heating Function

Understand the Anti-Cold Air Function

Understand the Compressor Crankshaft Heater Control Function

Understand the Heating Fan Delay Function

Understand the Indoor Coil Anti-Freezing Function

Understand the Passive Dehumidification Function

Understand the Refrigerant Leak Detection Function

Vertex Ducted Central Split Systems

Functions & Modes Explained

Determine the Breaker Size & Wire Needed for Your System

Diagnose & Prevent Crossed Wiring in Multi-Zone Systems

Understand how the System Receives Power

Electrical Related Queries

Maintenance Tips

Operation & Usage

P4 Error Code (Quantum Series)Updated 8 days ago

Introduction

Troubleshooting Diagram