P0AA6

P0AA6 indicates the BECM has detected an electrical isolation fault between the high-voltage battery pack (and its associated cabling, inverter, MG1/MG2) and the vehicle chassis — the isolation resistance has dropped below the safety threshold (typically 100 ohms per volt, so a 200V Prius pack requires 20K ohms minimum to chassis, a 360V Volt pack requires 36K ohms). This is a SAFETY code; the orange HV cables and the pack itself are now leaking current to the chassis at a level that could shock a technician. Cheapest-first diagnostic ladder: do NOT probe HV components without PPE and an insulation tester. Start with a visual inspection (12V system disconnected, service plug pulled, 10-minute capacitor discharge wait) of all orange HV cable connectors for moisture, green corrosion, or damaged insulation. Caveat: P0AA6 can be triggered by a wet 12V/HV junction box after a car wash or heavy rain, and will self-clear after the area dries — but if it returns, do not ignore it; coolant intrusion into the pack is a thermal-runaway risk on lithium platforms.

Vehicle-specific patterns: 2010-2015 Toyota Prius Gen 3 (ZVW30) — HV battery coolant intrusion from leaking inverter coolant hose dripping onto pack lid; Toyota TSB T-SB-0023-15 inspects and reseals. 2011-2015 Chevrolet Volt — coolant leak from the battery thermal management loop into the pack itself (lithium-ion T-pack) triggers P0AA6 with companion P1FFF; GM safety recall 15V-145 covered some VINs. 2005-2012 Ford Escape Hybrid — HV cable insulation degradation at the inverter connector from underhood heat cycling. 2013-2018 Ford Fusion Hybrid — HV junction box water intrusion from cowl drain blockage. Estimated repair: $380 to $7,200.