Phase sequence error
The L31 error code on Toshiba boilers indicates phase sequence error.
Toshiba L31 means: phase sequence error. The usual cause is abnormal phase sequence in the power system. You can safely reset the boiler once — if L31 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does L31 Mean
The L31 code is shown by the boiler’s control board when it detects phase sequence error. 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 |
|---|
| The display shows L31 and the boiler stops until the fault is cleared |
Common Causes
Causes documented in the Toshiba service literature published by centriassistenza.org, cross-checked against the manufacturer’s fault-code table.
| Cause |
|---|
| Abnormal phase sequence in the power system |
Safety Warning
L31 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
Consult service manual
Refer to the Toshiba service documentation for the specific diagnosis procedure for fault code L31.
Check error log
Access the boiler error log to check for related fault codes that may help identify the root cause.
Contact manufacturer support
If the fault persists after basic checks, contact Toshiba technical support for specialist guidance.
How to Fix It
Have this checked: Abnormal phase sequence in the power system
Refer to the Toshiba service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Toshiba models that can display fault code L31:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Toshiba models | — | Possible |
Frequently Asked Questions
L31 is not classified as a high-severity fault, so the boiler can be reset once. If L31 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.