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OBD-II Code

P0AF2

Severity

Not yet reviewed

Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.

Can you drive it

We cannot say

Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.

Indicative cost (USD)

$2,500–$5,000

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

$2,500 to $5,000 (reman pack or in-pack relay/precharge assembly + Class-0 labor).

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.

How a shop works this

Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.

  1. Note every code that is set, not just this one.

    Codes that appear together usually narrow the cause faster than any one of them read alone.

  2. Read the freeze frame — the conditions the fault was recorded under.

    Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.

  3. Confirm the fault is current rather than history.

    Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.

  4. Then follow the diagnostic notes further down this page, in the order they are written.

    They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.

If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.

Common symptoms

  • Check engine light
Read the full diagnostic procedureP0AF2 means the BMS detected that the negative high-voltage contactor (the main relay that connects pack-negative to the inverter HV bus return path)…

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 patterns2004-2009 Toyota Prius Gen2 and 2006-2013 Lexus RX400h/RX450h see negative-contactor welds at the same rate as positive-contactor welds, and the Pana…
  • 2004-2009Toyota 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.
  • 2003-2011Honda Civic Hybrid IMA sees contactor welds from frequent stop/start cycling.
  • 2011-2017Nissan 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.
  • 2013-2017Ford 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).

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