DIY HVAC Tools

Carrier mini split error code P5

Mode conflict (multi-zone).

  • TypeProtection
  • SystemOperation
  • Can I fix it?Usually a homeowner fix
  • Applies toindoor display, classic two-character codes (38MHRB, 38MGR, 40MAQ)

What P5 means on a Carrier

On a multi-zone system, one indoor unit is asking for heating while another asks for cooling. The outdoor unit can only do one at a time, so the conflicting zone shows P5 and waits.

On this platform, P5 is a protection: the system stopped or throttled itself to prevent damage; many clear on their own once conditions return to normal.

Common causes

  • Two zones set to opposite modes.
  • A zone left in Auto mode that flipped to the opposite mode of the others.

How to fix it yourself

You can almost always clear this yourself with the steps below.

  1. Set every indoor unit to the same mode (all Cool, all Heat, or all Dry). Fan-only mode does not conflict.
  2. Avoid Auto mode on multi-zone systems; it is the usual cause of the conflict.
  3. The first zone to call sets the mode for the whole system.

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

Not a fault. No technician needed.

Which Carrier units show P5

This page applies to Carrier Comfort 38MHRB / 40MHHQ, Comfort 38MGR / 40MGQ, Performance 40MAQ / 38MAQ, Infinity 40MPHA / 38MPRA and Carrier multi-zone units on the indoor display, classic two-character codes (38MHRB, 38MGR, 40MAQ). Carrier's own documentation lists P5 as "Mode conflict (multi-zone)", the same definition used across the Midea platform (classic codes) 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 Carrier shows this code

indoor display, classic two-character codes (38MHRB, 38MGR, 40MAQ): The code appears on the indoor unit's LED display in place of the set temperature. Some models also blink the indicator lamps in a pattern that matches the code. E codes are faults in the indoor unit or its communication link, F codes are faults on the outdoor side, and P codes are protections: the outdoor unit has stopped itself to prevent damage. EC is the refrigerant leak check.

Other Carrier codes

Same part of the system as P5:

P3Outdoor temperature too low protection (heating lockout)
E0Indoor unit EEPROM parameter errorE1Communication error between indoor and outdoor unitsE2Zero-crossing signal detection errorE3Indoor fan speed out of control (indoor fan motor fault)E4Indoor room temperature sensor (T1) open or short circuitE5Evaporator coil temperature sensor (T2) open or short circuitECRefrigerant leak detected (low refrigerant charge)F0Overload current protection (compressor over-current)

All Carrier error codes

P5 on other brands

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

  • Pioneer P5 Mode conflict (multi-zone) / Condenser high temperature protection (outdoor display)
  • Blueridge P5 Compressor current protection / Mode conflict (multi-zone)
  • Gree P5 Compressor current protection
  • Zone Air P5 Cooling mode sub-cooling (anti-freeze) protection
  • Mitsubishi Electric P5 Drain pump fault (overflow protection)
  • Trane P5 Cooling mode sub-cooling (anti-freeze) protection / Drain pump fault (overflow protection)
  • Arctic King P5 Mode conflict (multi-zone)
  • Heil P5 Mode conflict (multi-zone) / Compressor current protection
  • ACiQ P5 Mode conflict (multi-zone) / Cooling mode sub-cooling (anti-freeze) protection

Questions people ask

Can I reset a Carrier P5 code myself?

Yes. Turn the system off at the breaker for five minutes, then restart it. If P5 comes back, the fault is real and needs the checks above.

Is it safe to keep running a Carrier showing P5?

Not repeatedly. A protection code means the unit stopped itself to prevent damage, and resetting it over and over can turn a cheap repair into a compressor failure. Reset once, check the basics, and stop if it returns.

Do I need a technician for Carrier P5?

You can almost always clear this yourself with the steps below. Not a fault. No technician needed.

Sources

  • Carrier 38MHRB Single Zone Ductless Service Manual SG-38MHRB-01 (Diagnosis and Solution section)
  • Carrier 40MAQ / 38MAQ High-Wall Ductless Service Manual 40MAQ-01SM (Diagnosis and Solution section)
  • Carrier 40MPHA / 38MPRA Infinity High Wall Ductless Service Manual (error code table)

Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.