How do I clear an error code from my Rheem Tankless Water Heater?

First, turn off all hot water faucets and press the Power ON/OFF button to turn off the water heater. Wait 5 minutes, then restart and turn on a hot water faucet to check the display. If the error persists, unplug the unit for 30 seconds, plug it back in, and repeat the process. If the error code still remains after this, contact customer service for assistance.