P0AF1

P0AF1 means the BMS detected that the positive high-voltage contactor (the main relay that connects pack-positive to the inverter HV bus) is stuck closed — it failed to open when commanded off during shutdown, or it read voltage on the bus when the contactor coil was de-energized. This is a serious code. A stuck-closed contactor means the orange-wire HV bus may remain live AFTER the vehicle is shut off and even after the service plug is removed; depending on the platform, capacitor bleed-down can take 5-10 minutes but the contactor weld will keep the bus hot indefinitely. Shop-floor ladder: (1) Verify with the scan tool — most platforms log contactor-state during the last 10 ignition cycles and can confirm stuck-closed vs intermittent. (2) DO NOT open the pack or touch any orange wiring until you have measured HV bus voltage with an HV-rated CAT III/IV 1000V meter and confirmed the bus is at safe potential. (3) Coil-resistance test the contactor at the BMS plug — typical coil R is 5-30 ohms at room temp; a welded contactor often reads normal coil R because the failure is mechanical, not electrical. (4) Drop-voltage test across the contactor terminals: 0V means open (correct when commanded off); battery-pack-voltage means closed (correct when commanded on); intermittent or sticking is the failure mode. (5) Almost all platforms require pack replacement or pack-internal contactor replacement at a specialist — this is not a roadside fix. 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: any high-voltage traction-pack platform can throw P0AF1, but the common offenders are 2004-2009 Toyota Prius Gen2 and 2006-2013 Lexus RX400h/RX450h where the in-pack Panasonic relay assembly welds shut after repeated high-current events (typically aggressive regen or hot-climate fast-charging on later platforms); the BMS reports the weld and the pack is condemned. 2003-2011 Honda Civic Hybrid IMA contactor welds happen at lower mileage because the IMA system cycles contactors more frequently than a full-hybrid. 2011-2017 Nissan Leaf Gen1 sees this from corrosion on the contactor coil drive circuit. 2011-2015 Chevy Volt Gen1 and 2016-2019 Volt Gen2 see contactor stuck-closed from BECM (battery energy control module) drive-stage failure rather than mechanical weld — sometimes a BECM software update or module swap resolves it. Plug-in Prius and Ford C-Max Energi see the same. Estimated repair: $2,500 to $5,000 (reman pack or in-pack relay assembly + Class-0 labor).