mypros+
Error code reference

Mitsubishi Air Conditioner Error Code E.2

Option fault

Mitsubishi codesMitsubishi air conditioner codes

Option fault - contact fault between inverter and plug-in option at connector 2.

First step from the service manual

Check that the plug-in option is plugged into connector 2 properly.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

MyPros+ Max

Get the full diagnostic procedure for E.2.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What E.2 means on a Mitsubishi air conditioner

The E.2 error code on a Mitsubishi air conditioner indicates an option fault caused by a contact failure between the inverter board and a plug-in option module at connector 2. This is a communication and power interface fault, meaning the inverter cannot properly detect or communicate with the accessory module that should be seated at that specific connector position. Plug-in option modules can include demand controllers, zone controllers, or communication interface boards, depending on the system configuration.

The fault is almost always tied to the physical connection at connector 2. If the plug-in option module is not fully seated, has been jarred loose, or has corroded or damaged pins, the inverter will register the absence or instability of that connection and trigger E.2. The error can also appear if the plug-in option module itself has failed internally, even when the connector appears secure.

Diagnosing this code begins with a thorough inspection of connector 2 on the inverter board. The module should be pressed firmly into the connector until it is fully engaged, with no gap between the module housing and the board. If reseating the module does not clear the fault, inspect the connector pins on both the module and the inverter for bent contacts, corrosion, or debris. A damaged connector or failed option module will require component replacement to resolve the fault.

Source: manufacturer service documentation.

Common causes of E.2

  1. 01

    Plug-in option not fully seated at connector 2

    Wiring / connection

    The most frequent cause is a module that was never fully pressed into connector 2, or one that has vibrated loose over time. Visually inspect and firmly reseat the module to confirm it is fully engaged.

  2. 02

    Corroded or dirty connector pins

    Wiring / connection

    Moisture or dust on the connector pins at either the inverter board or the plug-in module can cause intermittent or complete contact failure. Inspect pins carefully for oxidation or debris and clean as needed.

  3. 03

    Bent or damaged connector pins

    Part replacement

    Physical damage to the pins on connector 2 or on the module itself can prevent a reliable electrical connection. A bent pin is often visible on close inspection and may require connector or board replacement.

  4. 04

    Failed plug-in option module

    Part replacement

    If the connector and pins appear undamaged and the module is fully seated but the fault persists, the option module itself may have failed internally. Replacing the module is required to resolve this.

  5. 05

    Damaged inverter board connector 2 socket

    Part replacement

    In rare cases, the connector socket on the inverter board is cracked or damaged, preventing proper contact even with a known good module. This would require inverter board repair or replacement.

See the test procedure for each cause

Frequently asked questions about E.2

What does E.2 mean on a Mitsubishi air_conditioner?
E.2 indicates an option fault, specifically a contact failure between the inverter board and a plug-in option module at connector 2. The inverter cannot detect a proper connection to the accessory module that should be installed at that connector position. This is typically a physical connection issue rather than a refrigerant or electrical supply problem.
How do I fix an E.2 error on my Mitsubishi air conditioner?
Start by locating connector 2 on the inverter board and confirming the plug-in option module is fully and firmly seated. If the module appears loose, remove it and press it back in until it is fully engaged. If the fault remains after reseating, inspect the connector pins for corrosion or damage, and consider having the module or inverter board tested by a qualified technician.
Is it safe to run my Mitsubishi air conditioner with an E.2 error?
An E.2 fault is a control communication error and does not typically indicate a refrigerant leak or immediate electrical hazard. However, the system may not operate correctly or may be locked out until the fault is resolved. It is best to address the error promptly rather than attempting to continue running the unit.
Will resetting the unit clear the E.2 error code?
A power reset may temporarily clear the E.2 code, but if the underlying connection fault at connector 2 has not been corrected, the error will return when the system restarts and checks the option interface. The fault must be resolved at the connector before a reset will provide a lasting result.
How much does it cost to repair an E.2 error on a Mitsubishi air conditioner?
If the fix is simply reseating the plug-in option module, the cost is primarily a service call fee, typically in the range of $75 to $150 depending on your location. If the option module needs replacement, parts and labor together could range from $150 to $400 or more. Inverter board replacement, if required, would be at the higher end of the repair cost spectrum.

Related Mitsubishi air conditioner codes

All Mitsubishi air conditioner codes
View all 79 Mitsubishi air conditioner codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass