What steps should I take if my heat pump shows an E1 error code?

For an E1 error, which indicates compressor high pressure protection, check the liquid valve and gas valve of the outdoor unit to ensure they are fully open. Verify correct wiring for the high-pressure switch and confirm that both indoor and outdoor fans are operating correctly. Ensure there's no blockage in air outlets or return ports. The ambient temperature should also be within normal range and not too high, with no system overcharging or refrigerant line blockages detected. (Page 26)