Safety first: Turn OFF power and gas. Allow the unit to cool. Gas and ignition components should be serviced carefully.

Check gas supply: Confirm the gas shutoff valve is open and other gas appliances are working. If not, contact your gas supplier.
Inspect flame rod and igniter: Remove the burner access panel as per Rheem manual. Locate the flame rod and igniter. Clean the flame rod with fine emery cloth to remove soot. Ensure proper gap and alignment per specifications.
Check wiring: Verify all ignition and flame sensor wires are firmly connected and not damaged.
Observe ignition (advanced): With covers in place as required, restore power and call for hot water. Look through the sight glass for spark and flame. If there is no spark, the igniter or ignition module may be faulty.
If E9 persists: Replacement of the igniter, flame rod, or control board may be required. This is best handled by a qualified technician due to combustion safety concerns.

Rheem tankless water heater displays E9 and will not operate

Possible Causes