AC Error Codes · Mitsubishi Electric
Mitsubishi Electric AC Error Codes: Mr. Slim & City Multi Explained
Find your code, understand what it means, then run a guided diagnosis.
Error Code Finder
Look a code up against sourced manufacturer records. Codes we cannot source are not listed — a guessed meaning is worse than no meaning.
Mitsubishi Electric is unusual: it maintains three structurally different code systems across its product lines, and the same fault can display differently depending on where you read it. Knowing which system you are looking at matters more than the code itself. Note: Mitsubishi Electric and Mitsubishi Heavy Industries are separate manufacturers with entirely different code systems.
How do Mitsubishi Electric error codes work?
Mitsubishi Electric uses three separate systems: two-character E/P codes on Mr. Slim residential splits, four-digit numeric M-NET codes on City Multi VRF systems (shown on the outdoor PCB display and centralized controllers, with a parallel two-digit legacy code on older indoor receivers), and LED flash-count sequences on legacy P-series boards. Identify which display is showing the code before looking it up.
Product families covered
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Mr. Slim (residential split / ducted / cassette)
Two-character E/P alphanumeric codes.
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City Multi (VRF)
Four-digit M-NET codes on the outdoor 7-segment display and AE-200 / GB-50 / EW-50 controllers; older indoor receivers show a parallel two-digit legacy code for the same fault.
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Legacy P-series boards
LED flash-count sequences rather than alphanumeric codes.
Where the code is displayed — and why it matters
The same fault can be labelled differently depending on which display you read it from, so identify the display before looking the code up.
- Mr. Slim wall controller or receiver
- Two-character E/P code — a residential split code.
- City Multi outdoor PCB / AE-200, GB-50, EW-50
- Four-digit M-NET code, usually with the affected unit address.
- Older City Multi indoor receiver
- Two-digit legacy code describing the SAME fault as the four-digit code — parallel labels, not different faults.
- Legacy P-series board LEDs
- A flash-count sequence; count the flashes rather than looking for characters.
Which code system are you looking at?
The display location identifies the system — Mitsubishi's own documentation separates codes by where they appear:
- E / P + digit
- Mr. Slim split system code (wall controller or receiver)
- 4-digit number
- City Multi M-NET code (outdoor PCB display or centralized controller)
- 2-digit number
- City Multi legacy format on older indoor receivers — same faults, different labels
- LED flashes
- Legacy P-series board diagnostics (flash-count sequence)
How the families differ
- Mr. Slim faults are confined to one indoor/outdoor pair; City Multi faults travel on the shared M-NET bus and can therefore appear across many zones at once.
- The same City Multi fault has a four-digit and a two-digit label depending on where you read it. Record both if both are visible.
- Mitsubishi Heavy Industries is a different manufacturer with an E0x numeric system and its own LED patterns — its codes must never be read against these tables.
Documented City Multi (M-NET) codes
City Multi runs on the M-NET communication bus, so communication codes can cascade across multiple zones at once. Mr. Slim E/P tables are in technical review and will publish once verified against official documentation.
| Code | What it reports | Applies to | Severity | Source |
|---|---|---|---|---|
| 1302 | Indicates communication error that can be triggered by an indoor-unit rotary-switch address conflict even when the bus wiring is intact | City Multi VRF | Moderate | A |
| P6 / P9 | Indicates addressing or M-NET bus-wiring problems that can affect several zones simultaneously | City Multi VRF | Moderate | B |
Before you act on a code
- Mitsubishi Electric and Mitsubishi Heavy Industries are different manufacturers — MHI uses an E0x numeric system and LED flash patterns that do not match Mitsubishi Electric tables.
- The 4-digit and 2-digit City Multi formats describe the same faults with different labels — they are parallel, not interchangeable.
- The full Mr. Slim and City Multi code tables are in technical review against Mitsubishi Electric's official documentation before publication.
Official manufacturer documentation
How to identify your system
- Check where the code displays: wall controller (Mr. Slim), outdoor PCB 7-segment or AE-200/GB-50/EW-50 controller (City Multi 4-digit), older indoor receiver (City Multi 2-digit legacy).
- One outdoor unit serving many indoor units across rooms or floors indicates City Multi VRF.
- Confirm the brand plate says Mitsubishi Electric, not Mitsubishi Heavy Industries.
No code showing? Start from the symptom
Mitsubishi Electric error codes — common questions
Why does my controller show a different code than the outdoor unit?
On City Multi systems the same fault can display as a four-digit M-NET code on the outdoor PCB and centralized controllers, and as a two-digit legacy code on older indoor receivers. They are parallel formats for the same fault — record both if you can see both.
My whole floor shows communication errors at once — why?
City Multi zones share the M-NET communication bus. Addressing or bus-wiring faults can cascade across every zone on the circuit, which is why multi-zone simultaneous errors usually point to the network rather than the individual units.
Are Mitsubishi Electric and Mitsubishi Heavy Industries codes the same?
No. They are separate manufacturers. Mitsubishi Heavy Industries uses its own E0x numeric prefix system and model-family-specific LED flash patterns that must not be read against Mitsubishi Electric tables.
Need this looked at properly?
Call or send a photo on WhatsApp and we will tell you whether it needs an inspection, and what the work involves, before anyone travels.
Sources consulted
- Mitsubishi Electric Asia official Mr. Slim error-code spreadsheet
- Mitsubishi Electric Asia official City Multi error-code tables (V2, V3, V4 and unversioned releases — internally consistent)
- Independent City Multi / M-NET technical documentation (cross-validation)