P0A9C: Hybrid/EV Battery Temperature Sensor A Circuit Range/Performance
What to do
Often symptomless — but the pack's thermal management is running on a vote with one bad voter. Worth fixing without urgency.
What this code means
The battery temperature reading is electrically alive but implausible — stuck, drifting, or disagreeing with the pack's other sensors.
Multiple thermometers make this variant easier to catch than most: one sensor reading ten degrees adrift of its neighbours convicts itself. The consequence and diagnosis are P0A9B's.
Likely causes
Start here
- Faulty battery temperature sensor · specialist
- Sensor drifted out of calibration · specialist
Less common
- Corroded or loose connector · easy
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
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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