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Lennox Mini-splits: MLB / MPC / 3PC outdoor with M22A, M33C, MWMC, MCFA/B, MFMA indoor Error Codes
Older Lennox mini-splits show short codes (for example E1); newer ones show the longer form (EL 01). Old codes are listed in parentheses only where Lennox's manual pairs them consistently. Ducted MMDB units with wired remotes use a different display.
| Code | Meaning | What to check |
|---|---|---|
| EH 00 | Indoor EEPROM fault. | Indoor control board. |
| EL 01 (E1) | Indoor/outdoor communication fault. | Interconnect wiring, connections, outdoor power. How to fix → |
| EH 03 (E3) | Indoor fan speed fault. | Indoor fan motor, wheel binding, connector. |
| EH 60 | Indoor room temperature sensor (T1) fault. | Measure the sensor; check connector. How to fix → |
| EH 61 | Indoor coil temperature sensor (T2) fault. | Measure the sensor; check connector. How to fix → |
| EL 0C (EC) | Refrigerant leak detection (cooling mode). | Leak search, flare joints; service valves fully open. How to fix → |
| PC 08 (F0) | Outdoor current overload. | Supply voltage, dirty coils, compressor, overcharge. How to fix → |
| EC 53 (F1) | Outdoor ambient temperature sensor (T4) fault. | Measure the sensor; check connector. How to fix → |
| EC 52 (F2) | Outdoor coil temperature sensor (T3) fault. | Measure the sensor; check connector. How to fix → |
| EC 54 (F3) | Compressor discharge temperature sensor fault. | Measure the sensor; check connector. How to fix → |
| EC 51 | Outdoor EEPROM fault. | Outdoor control board. |
| EC 07 (F5) | Outdoor fan speed fault. | Outdoor fan motor, obstruction, connector. |
| EC 72 | Outdoor DC fan lack-phase fault. | Fan motor wiring and outdoor board. |
| PC 00 (P0) | IPM module error. | Supply voltage, outdoor airflow, compressor, inverter board. How to fix → |
| PC 01 (P1) | High or low voltage protection. | Supply voltage under load. How to fix → |
| PC 02 (P2) | High temperature at compressor top. | Low charge, restriction, outdoor airflow. How to fix → |
| PC 0L (P3) | Outdoor low ambient protection. | Normal in very cold weather. |
| PC 04 (P4) | Compressor drive error. | Compressor wiring and windings, inverter board. How to fix → |
| PC 43 | Compressor lack-phase protection. | Compressor U-V-W wiring, inverter board. How to fix → |
| PC 45 | Outdoor IR chip drive failure. | Outdoor inverter board. How to fix → |
| - - | Mode conflict (multi-zone). | Set all indoor units to the same mode. |
| CP | Remote switched off (status, not an error). |
How to read the codes
- EH = indoor, EC = outdoor, EL = communication or refrigerant, PC = protection (compressor, inverter, voltage).
- 'CP' means the unit was switched off by a remote switch, and '- -' is a multi-zone mode conflict; neither is a component failure.
- Codes EC 72, PC 43 and PC 45 appear only on newer units with the long-form display.
Codes point to a circuit, not a part. Test before replacing boards or sensors. Inverter boards hold a dangerous charge after power-off; wait and verify DC bus voltage is gone before touching them. Refrigerant work requires EPA 608 certification.
Source: Lennox Mini-Split Systems Service Manual 100030 (4/2022), Indoor and Outdoor Unit Error Codes. The "meaning" column follows the manufacturer's wording; "what to check" is our field summary. Always go by the label on the furnace you're working on.
Related
- Mini-split communication error troubleshooting
- Mini-split flare connections (the usual leak point)
- Look up any mini-split code
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