State tankless water heater displays E03 and shuts down; fan may start but burner does not light.

Safety: Turn off power and gas. Do not operate the heater with suspected vent blockage due to carbon monoxide risk.

• Inspect vent termination: Go outside and check the exhaust and intake terminals. Remove leaves, snow, bird nests, or debris. Ensure clearances per State installation manual are maintained.
• Check intake screen: On direct-vent models, remove and clean any intake air screens or filters with a soft brush and mild detergent. Rinse and dry completely before reinstalling.
• Exhaust fan and pressure switch: Remove the front cover. Verify the combustion blower spins freely by hand and is not obstructed by debris. Inspect the rubber tubing to the air pressure switch for kinks, cracks, or water. Re-seat tubing and connectors.
• Reset and test: Restore power and gas, then run hot water. If E03 persists, the pressure switch or combustion blower motor may be faulty and should be tested with a multimeter by a qualified technician.