Protect mode is caused by one of three things:

1. Overheating caused by lack of ventilation;
2. Incorrect wiring of speakers, (ie. not impedance matched or poor wiring condition);
3. Faulty receiver.

Make sure that the unit is not withing a confined cabinet etc., disconnect all speaker wiring and see what happens. If it still enters protect mode, then unit will need servicing.

For a dealer in your area, [Link: onkyousa.com]