Water heater locks out with error 02; burner lights briefly then shuts down.

Safety: Switch off power and close the gas valve before opening the casing.

• Clean ionization electrode: Locate the flame detection (ionization) electrode. Remove light surface oxidation with fine abrasive pad. Ensure the ceramic is intact and the metal rod is not bent away from the flame path.
• Check grounding: Verify that the burner assembly and the ionization electrode bracket have a solid ground connection to the chassis. Tighten any loose screws and clean off corrosion.
• Inspect gas pressure stability: If other gas appliances flicker or go out, there may be a supply issue. Do not attempt to adjust the gas valve yourself; contact a licensed gas technician.
• Check wiring to control board: Ensure the ionization electrode lead is firmly connected to the main control board terminal and not damaged or burnt.
• Reset and test: Restore gas and power, reset the unit, and run hot water. If the error persists, the control board flame detection circuit or gas valve modulation coil may be defective.

Professional help: Flame signal diagnostics often require a multimeter and manometer. If you are not experienced, contact an authorized Immergas technician.