OBD-II Code
P0AF1
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 assembly + Class-0 labor).
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.
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.
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.
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.
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.
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 procedureP0AF1 means the BMS detected that the positive high-voltage contactor (the main relay that connects pack-positive to the inverter HV bus) is stuck cl…
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
- Verify with the scan tool — most platforms log contactor-state during the last 10 ignition cycles and can confirm stuck-closed vs intermittent.
- 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.
- 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.
- 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.
- 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 patternsany high-voltage traction-pack platform can throw P0AF1, but the common offenders are 2004-2009 Toyota Prius Gen2 and 2006-2013 Lexus RX400h/RX450h w…
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.
- 2003-2011Honda Civic Hybrid IMA contactor welds happen at lower mileage because the IMA system cycles contactors more frequently than a full-hybrid.
- 2011-2017Nissan Leaf Gen1 sees this from corrosion on the contactor coil drive circuit.
- 2011-2015Chevy 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).
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