E4 displayed and burner will not ignite on gas Giant water heater

Safety first: Turn gas control to OFF and disconnect electrical power. Wait for the burner area to cool completely.

• Locate flame sensor: On Giant gas models with electronic ignition, the flame sensor is a small metal rod positioned in the burner flame, usually combined with the igniter or separate but adjacent.
• Clean the sensor: Remove the flame sensor mounting screw and gently pull out the rod. Lightly clean the rod with fine steel wool or a Scotch‑Brite pad to remove oxidation. Do not sand aggressively.
• Inspect wiring: Check the flame sensor lead from the rod to the control board for cracks, burns, or loose connections. Reseat the connector at the control.
• Check burner flame: With covers reinstalled, restore gas and power, and observe ignition through the sight glass. Flame should be steady and blue. Yellow or weak flame may indicate dirty burner or low gas pressure—have a gas technician service it.
• Replace sensor or control: If cleaning and wiring checks do not resolve E4, replace the Giant flame sensor. If the issue persists, the control board may need replacement by a qualified technician.