Get the Prius KEY
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Start the Prius
Press Climate button on center console and turn climate control OFF
Press PWR button on center console to turn audio system OFF
Turn Argus OFF by holding the knob in for several seconds
NOTE: There are high voltages present on the connector. Although it isn't easy to touch the contacts, it's not impossible. Be careful.
Look on top of the UPS in the furnace room. There is a box with two meters next to each other. The right-hand meter (UPS battery) should always be reading about 2/3 full scale (relative reading). When the Prius is connected and turned ON, the left-hand meter should also be reading about 2/3 full scale.