mypros+
Error code reference

Mitsubishi Air Conditioner Error Code E.6

CPU fault variant (Fault 6).

Mitsubishi codesMitsubishi air conditioner codes

CPU fault variant (Fault 6).

First step from the service manual

Check for devices producing excess electrical noises around the inverter.

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.6.

  • 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.6 means on a Mitsubishi air conditioner

The E.6 error code on a Mitsubishi air conditioner indicates a CPU fault variant, specifically classified as Fault 6. This code points to a communication or processing error within the inverter control board's central processing unit. The inverter CPU is responsible for managing compressor speed, monitoring sensor inputs, and executing control logic. When electrical noise or interference disrupts the CPU's normal operation, the unit triggers this fault to protect itself from running in an undefined or unsafe state.

The primary diagnostic focus for E.6 is electrical noise interference near the inverter unit. Devices such as variable frequency drives, large motors, uninterruptible power supplies, or other inverter-based equipment operating in close proximity can inject high-frequency noise into the power supply or signal lines. This interference can corrupt CPU data processing or cause the control board to receive false signals, leading to a fault condition. Grounding issues within the unit or building electrical system can also amplify susceptibility to this type of interference.

Beyond external noise sources, the fault can also originate from internal issues on the inverter control board itself, including solder joint failures, capacitor degradation, or a failing CPU component. Power supply instability, such as voltage fluctuations or spikes on the incoming line, can produce similar symptoms. A thorough diagnosis should address external interference sources first before condemning the control board.

Source: manufacturer service documentation.

Common causes of E.6

  1. 01

    Electrical noise from nearby equipment

    Wiring / connection

    Devices such as variable frequency drives, large motors, or other inverter-based appliances operating near the unit can inject electrical noise into the power or signal lines, disrupting the CPU. Identify any such equipment installed or recently added near the inverter.

  2. 02

    Poor or inadequate grounding

    Wiring / connection

    A missing or high-resistance ground connection on the unit or within the electrical panel increases susceptibility to interference and can cause CPU faults. Check all ground connections at the unit terminal block and the main panel.

  3. 03

    Unstable or fluctuating supply voltage

    Wiring / connection

    Voltage spikes or sags on the incoming power supply can disrupt CPU operation and trigger fault codes. Measure the supply voltage at the unit under load to confirm it falls within the rated tolerance.

  4. 04

    Faulty inverter control board

    Part replacement

    Degraded capacitors, failed solder joints, or a failing CPU chip on the inverter control board can produce this fault internally. This is typically identified after ruling out external electrical causes.

  5. 05

    Damaged or corrupted internal wiring connections

    Wiring / connection

    Loose or corroded connector pins on the control board harness can cause intermittent signal errors that register as a CPU fault. Inspect all connectors to the inverter control board for secure seating and corrosion.

See the test procedure for each cause

Frequently asked questions about E.6

What does E.6 mean on a Mitsubishi air_conditioner?
E.6 is a CPU fault variant, classified as Fault 6, on Mitsubishi air conditioners. It indicates the inverter control board's CPU has detected an error and shut down operation as a protective measure. The most common trigger is electrical noise from nearby equipment interfering with the inverter electronics. A qualified technician should inspect the electrical environment and the control board to diagnose the root cause.
Can I fix a Mitsubishi E.6 error code myself?
Some steps, such as identifying and removing nearby electrical equipment that produces interference, are accessible to a knowledgeable homeowner. However, checking supply voltage, inspecting the inverter control board, and verifying grounding connections involve working with high-voltage components and should be performed by a qualified technician. Attempting internal repairs without proper training and safety equipment is not recommended.
Is it safe to keep using my air conditioner when E.6 is displayed?
No. The E.6 fault causes the unit to shut down and it will not operate normally while the code is active. Attempting to force operation in a fault state could risk further damage to the control board or other components. The unit should remain off until the fault is diagnosed and resolved.
How much does it cost to repair a Mitsubishi E.6 error?
Repair costs vary widely depending on the root cause. If the issue is resolved by addressing external electrical interference or grounding, costs may be limited to a service call fee, typically ranging from $75 to $150. If the inverter control board requires replacement, parts and labor combined can range from $300 to $700 or more depending on the model and local labor rates.
Will resetting the unit clear the E.6 error code?
A power reset may temporarily clear the E.6 code and allow the unit to restart, but if the underlying cause, such as electrical noise or a failing control board, is still present, the fault will return. Resetting without diagnosis is not a fix and repeated faults can indicate a worsening condition. A proper diagnosis should be completed to prevent recurring shutdowns.

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