Carrier mini split error code E2
Zero-crossing signal detection error.
- TypeFault
- SystemControl board
- Can I fix it?Homeowner checks, then maybe a tech
- Applies toindoor display, classic two-character codes (38MHRB, 38MGR, 40MAQ)
What E2 means on a Carrier
The indoor board times its fan and power circuits off the zero-crossing point of the AC supply. It lost that reference signal, which points to a power-quality problem or a board fault.
On this platform, E2 is a fault: something has failed or is disconnected and needs diagnosis.
Common causes
- Unstable or noisy supply power (a generator, a failing inverter, or a loose neutral).
- A loose power connection at the indoor terminal block.
- A failed zero-crossing detection circuit on the indoor main board.
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.
- 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.
- If the unit is running from a generator or a portable power station, try it on utility power.
- With power off, tighten every screw on the indoor terminal block.
- If you own a multimeter and are comfortable using it, measure the supply voltage at the outdoor unit's L1 and L2 terminals with the unit running. A 230 V system should read roughly 208 to 253 VAC.
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
If the supply is clean and the wiring is tight, the indoor main board is the culprit and needs replacing.
Which Carrier units show E2
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 E2 as "Zero-crossing signal detection error", 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 E2:
E2 on other brands
The same characters do not always mean the same thing. Check the brand on your unit.
- Pioneer E2 Zero-crossing signal detection error / Communication error between the outdoor unit and the indoor units (outdoor display)
- Blueridge E2 Indoor anti-freeze protection / Zero-crossing signal detection error
- Gree E2 Indoor anti-freeze protection
- Zone Air E2 Indoor fan coil (evaporator) temperature sensor fault (open or short circuit)
- Mitsubishi Electric E2 Remote controller control board fault
- Trane E2 Indoor fan coil (evaporator) temperature sensor fault (open or short circuit) / Remote controller control board fault
- Arctic King E2 Zero-crossing signal detection error
- Heil E2 Zero-crossing signal detection error / Indoor anti-freeze protection
- ACiQ E2 Zero-crossing signal detection error / Indoor fan coil (evaporator) temperature sensor fault (open or short circuit)
Questions people ask
Can I reset a Carrier E2 code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If E2 comes back, the fault is real and needs the checks above.
Is it safe to keep running a Carrier showing E2?
The unit will usually refuse to run, or run with reduced output, until the fault is cleared. Repeated resets do not fix anything and can mask a problem that is getting worse.
Do I need a technician for Carrier E2?
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician. If the supply is clean and the wiring is tight, the indoor main board is the culprit and needs replacing.
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.