P0AF2

P0AF2 means the BMS detected that the negative high-voltage contactor (the main relay that connects pack-negative to the inverter HV bus return path) is stuck closed — it failed to open when commanded off during shutdown, or it read continuity to the bus when de-energized. Same safety implication as P0AF1: the HV bus may remain live AFTER shutdown and after the service plug is removed, because removing the service plug only breaks the pack into two half-strings — if a contactor is welded the half-string nearest the inverter remains live. Shop-floor ladder: (1) Scan-tool confirm the stuck-closed event in BMS history. (2) Measure HV bus with an HV-rated meter before touching any orange wiring — even after service-plug removal. (3) Coil-resistance test the negative contactor at the BMS plug (5-30 ohms typical) and drop-voltage test the contactor (0V open / pack voltage closed). (4) Many platforms wire the negative contactor + a precharge resistor in series to limit inrush; a failed precharge resistor (10-50 ohms typical, open when burned) can cause repeated contactor arc-welding because the contactor closes onto an uncharged inverter capacitor bank — check the precharge circuit before pulling the contactor. (5) Repair is in-pack relay assembly or full pack replacement at a hybrid specialist. DO NOT probe HV orange-wire circuits with a standard multimeter. Always service HV with Class 0 1000V gloves, isolation tester (Megger), and DC-rated lugged probes. Pack contactor stuck-closed (P0AF1/P0AF2) is the only condition where the orange-wire bus may be live AFTER the service plug is removed. NEVER assume zero potential — always measure with an HV-rated meter.

Vehicle-specific patterns: 2004-2009 Toyota Prius Gen2 and 2006-2013 Lexus RX400h/RX450h see negative-contactor welds at the same rate as positive-contactor welds, and the Panasonic relay assembly contains both in one housing — when one welds, the other is typically near end-of-life so techs replace the full assembly. 2003-2011 Honda Civic Hybrid IMA sees contactor welds from frequent stop/start cycling. 2011-2017 Nissan Leaf Gen1 and 2011-2019 Chevy Volt Gen1/Gen2 typically throw P0AF1/P0AF2 together when the precharge resistor opens and the contactor closes onto a cold capacitor bank, arc-welding both. 2013-2017 Ford C-Max Energi and Fusion Energi share the Volt-era pattern. Estimated repair: $2,500 to $5,000 (reman pack or in-pack relay/precharge assembly + Class-0 labor).