Faulty evaporator sensor
The E2 error code on Mitsubishi boilers indicates faulty evaporator sensor. Symptoms include 4 noise has entered into indoor/, * check led display on the outdoor control, 2 noise has entered into power.
Mitsubishi E2 means: faulty evaporator sensor. On this component the documented failure modes are ntc evaporatore difettosa, the evaporator sensor has failed — short circuit or open circuit or wiring, connector or harness of the evaporator sensor damaged or loose. You can safely reset the boiler once — if E2 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does E2 Mean
The E2 code is shown by the boiler’s control board when it detects faulty evaporator sensor. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| 4 Noise has entered into indoor/ |
| * Check LED display on the outdoor control |
| 2 Noise has entered into power |
| 3 Noise has entered into outdoor |
Common Causes
The first cause below is the one the Mitsubishi service literature publishes for this code (source: centriassistenza.org). The others are the failure modes documented for the same component on other boilers, confirmed by 8 different manufacturers.
| Cause |
|---|
| NTC evaporatore difettosa |
| The evaporator sensor has failed — short circuit or open circuit |
| Wiring, connector or harness of the evaporator sensor damaged or loose |
Safety Warning
E2 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
1. Note the exact error code and check the manufacturer's installation and service manual for specific guidance. 2. Check all visible wiring connections for security and condition. 3. Power cycle the boiler — switch off at the mains for 30 seconds, then switch back on. 4. If the fault recurs, check the fault history for related or recurring codes. 5. Inspect the boiler for any obvious signs of damage, leaks, or unusual sounds
How to Fix It
Measure the resistance of the evaporator sensor with a multimeter and compare it against the manufacturer’s resistance-versus-temperature table; replace it if it is open circuit, short circuit or out of range.
Unplug and re-seat the connector of the evaporator sensor, then check the harness for chafing, corroded pins and breaks in continuity.
Refer to the Mitsubishi service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Mitsubishi models that can display fault code E2:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Mitsubishi models | — | Possible |
Frequently Asked Questions
Measure the resistance of the evaporator sensor with a multimeter and compare it against the manufacturer’s resistance-versus-temperature table; replace it if it is open circuit, short circuit or out of range. According to the technical documentation, this is the first check on the list for E2.
E2 is not classified as a high-severity fault, so the boiler can be reset once. If E2 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.