OBD-II Code
P0AC0
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)
$180–$1,600
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P0AC0 indicates a circuit fault on hybrid battery pack air-temperature sensor A — the BECM is reading an out-of-range voltage (open circuit, short to ground, or short to power) from the thermistor that monitors air entering or within the pack.
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 procedureP0AC0 indicates a circuit fault on hybrid battery pack air-temperature sensor A — the BECM is reading an out-of-range voltage (open circuit, short to…
P0AC0 indicates a circuit fault on hybrid battery pack air-temperature sensor A — the BECM is reading an out-of-range voltage (open circuit, short to ground, or short to power) from the thermistor that monitors air entering or within the pack. Most NiMH and lithium hybrid packs use 2-4 air-temperature sensors distributed through the pack to detect thermal stratification.
Cheapest-first diagnostic ladder
- pull live data and read all pack temperature sensors simultaneously — a healthy set should agree within 3C at rest after a cold soak; if sensor A reads -40C (open circuit pegged low) or 215C (shorted high) while the others read 22C ambient, the sensor or its wiring is the fault.
- The thermistors are NTC-type with nominal 10K ohms at 25C. Caveat: P0AC0 alone does not disable the hybrid system but it does force the BECM into a conservative thermal management mode (cooling fan on more aggressively, charge/discharge current limited), which on Prius Gen 2 reduces fuel economy by 3-5 MPG until fixed.
Vehicle-specific patterns2004-2009 Toyota Prius Gen 2 (NHW20) — pack temp sensor A harness chafe on the pack lid edge causes intermittent P0AC0 that worsens with vibration; r…
- 2004-2009Toyota Prius Gen 2 (NHW20) — pack temp sensor A harness chafe on the pack lid edge causes intermittent P0AC0 that worsens with vibration; repair harness routing and add loom protection.
- 2010-2015Toyota Prius Gen 3 — revised harness routing reduced this failure but the sensor itself sometimes fails internally; Toyota P/N G9281-47010.
- 2005-2012Ford Escape Hybrid — BECM internal multiplexer failure on the temperature input throws P0AC0 + P0AC4 together; Ford TSB 12-7-15.
- 2003-2011Honda Civic Hybrid — IMA pack temp sensor failure typically presents with IMA light plus reduced assist.
Estimated repair$180 to $1,600.
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