Goodman mini split error code P4

Common causes

• The inverter heat sink (radiation fin) temperature thermistor has failed (they do drift and fail with age and heat cycling).
• Its plug has worked loose from the control board, or a pin has corroded.
• The sensor lead is chafed, pinched or chewed, giving an intermittent open or short.
• The control board's sensor input has failed (rare compared with the sensor itself).

How to fix it yourself

Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician.

1. Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.
2. If the code comes straight back after a reset, the fault is real and not a glitch.
3. With power off, locate the inverter heat sink (radiation fin) temperature sensor on the inverter heat sink. Follow its lead back to the board and reseat the plug firmly.
4. Inspect the lead for damage along its whole length, especially where it passes through the chassis.
5. If you have a multimeter, unplug the sensor and measure its resistance. A reading near zero ohms (short) or infinite (open) confirms a bad sensor. Most mini split thermistors read roughly 5 to 20 kΩ at room temperature, so a value in that range with a steady drift as you warm it in your hand means the sensor is fine and the board is the suspect.
6. Replacement thermistors are inexpensive and plug in. Match the part number from the parts list for your model.

Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.

When to call a technician

Sensor swaps are a doable DIY job on most units. Call a technician if the sensor tests good and the code persists, because that points at the control board.

Which Goodman units show P4

This page applies to Goodman e-Series wall-mount (FTXNG indoor / RXNG outdoor) units. Goodman's own documentation lists P4 as "Inverter heat sink temperature sensor fault", the same definition used across the Daikin it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.

Where Goodman shows this code

Most Daikin wall units do not show the code on the unit; the operation lamp blinks. To read the code, point the remote at the unit, hold CANCEL (or Timer Cancel) for about 5 seconds until 00 shows, then press CANCEL repeatedly. Each press shows a code; when the unit gives a long continuous beep instead of two short beeps, the code on the remote is the stored fault. Units with a wired controller show the code directly. A and C codes are indoor-unit faults, E, F, H, J, L and P codes are outdoor-unit faults and protections, and U codes are system-level problems such as communication, power supply and refrigerant shortage.

Other Goodman codes

Same part of the system as P4:

All Goodman error codes

P4 on other brands

The same characters do not always mean the same thing. Check the brand on your unit.

• Pioneer P4 Inverter compressor drive error / Compressor discharge temperature protection (outdoor display)
• Blueridge P4 Inverter compressor drive error
• Zone Air P4 Excessive outdoor discharge temperature
• Daikin P4 Inverter heat sink temperature sensor fault
• Mitsubishi Electric P4 Drain sensor or float switch fault
• Trane P4 Excessive outdoor discharge temperature / Drain sensor or float switch fault
• ACiQ P4 Inverter compressor drive error / Excessive outdoor discharge temperature