CUSTOMER CONCERN The vehicle was towed in with a no-start condition and DTC P0AA6 for a high-voltage isolation fault. CAUSE The 12-volt auxiliary battery measured only 8.3 volts and would not retain a charge; the confirmed report also found sleep-current draw at approximately 0.03 mA. CORRECTION Remove and replace the failed 12-volt auxiliary battery, clear DTC P0AA6, and verify the vehicle enters READY mode normally.

CUSTOMER CONCERN The 12-volt battery is not charging and the DC/DC converter module stores DTC U3000:04. CAUSE The 12-volt battery failed and could not accept or maintain the converter's charging output. CORRECTION Remove and replace the failed 12-volt battery, clear DTC U3000:04, and verify the DC/DC converter charges the low-voltage system normally.

CUSTOMER CONCERN After an oil change and repeated maintenance-reminder reset attempts, the vehicle will not start although the combination meter and brake lamps operate. CAUSE The 12-volt battery became too weak to power the hybrid control system during the extended reset attempt. CORRECTION Remove and replace the weak 12-volt battery and verify normal READY mode and vehicle startup.

CUSTOMER CONCERN Vehicle will not enter ready mode after an oil change and repeated attempts to reset the maintenance reminder; the combination meter illuminates but the brake warning remains on. CAUSE The 12-volt battery discharged below the level needed to power the hybrid control system during the extended reminder-reset attempts. CORRECTION Remove and replace the failed 12-volt battery and verify the Prius enters ready mode and the maintenance reminder resets normally.

CUSTOMER CONCERN The 12-volt battery goes dead because of a 1.08-amp parasitic draw; removing engine-room junction-block fuse 13 drops the draw to 0.015 amp. CAUSE A rear reading light remained switched on and was difficult to notice, creating the parasitic load on the dome-fuse circuit. CORRECTION Switch off and correctly position the rear reading-light switch, then verify the parasitic draw remains at approximately 0.015 amp.