P0AC5: Hybrid/EV Battery Temperature Sensor B Circuit
What to do
As P0A9B — wiring first, the sensor is a pack-internal job, and neighbouring sensors usually identify the liar before anything is opened.
What this code means
The second of the pack's cell temperature sensors has failed its circuit checks.
P0A9B carries the family's whole argument — why the pack carries several thermometers, what the module does without one, and why the quiet cold-lying failure is the one that ages packs. Sensors B, C and D are that argument repeated at different positions through the pack; the letter says where, and position matters only in one way: the module can sanity-check a suspect sensor against its neighbours, which usually convicts the right one without opening anything.
Likely causes
Start here
- Open circuit in sensor wiring · moderate
- Corroded or loose connector · easy
Less common
- Faulty battery temperature sensor · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
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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