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critical Trane
Error Code E04
Gas valve not energized when it should be after 10 times, or gas valve relay stuck closed.
? What Causes This
Mechanical failure of the gas valve or wiring issues connecting to relays.
✓ How to Fix It
Check electrical connections for loose contacts. Replace faulty relay if necessary. Ensure power supply is stable.
Source: page 26 of the official manual
From the manual
This error code appears in:
Trane S9x1