P0AAC: Hybrid/EV Battery Pack Air Temperature Sensor A Circuit
What to do
Not urgent — fan control gets cruder while the reading is missing. Wiring and connector first; the sensor lives in the cooling ducting rather than inside the pack, so this is one of the range's cheaper repairs.
What this code means
The sensor measuring the battery's cooling air has failed its circuit checks — a different measurement from the cell temperature sensors at P0A9B, and the difference is the point.
Two air sensors bracket the pack: one reads the air going in, the other what comes out, and the difference between them is how hard the pack is working — the paired-sensor argument from P2182, applied to a battery. The intake reading also guards against a trap: on a hot day the fan is pulling hot cabin air, and blowing forty-degree air over a warm pack heats it, so the module needs to know what it is blowing before deciding the fan helps.
Losing an air sensor degrades fan control rather than causing anything acute. Wiring first, per the block's standing pattern — these sensors sit in the ducting, more reachable than the cell sensors inside the pack.
Likely causes
Start here
- Open circuit in sensor wiring · moderate
- Corroded or loose connector · easy
Less common
- Faulty battery temperature sensor · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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