P0BC2: Hybrid/EV Battery Temperature Sensor E Circuit
What to do
A temperature sensor fault changes what the car will allow the battery to do, so expect reduced power or slower charging even though nothing is wrong with the pack itself. Worth fixing for that reason alone. The falsely-low direction is the one that matters for safety, because protection that should step in will not.
What this code means
The fifth of the pack's temperature sensors has a circuit fault.
Sensors A to D are already written at P0AA1, P0AC5, P0ACA and P0AE7; what a fifth one buys is resolution, and the reason a pack needs it is that a battery does not have a temperature. Cells in the middle of the pack are surrounded by other cells and run hotter than those at the edges; cells nearest the coolant inlet run cooler than those at the outlet. A single reading would either miss the hot spot or condemn the pack for having one.
The consequence of a bad temperature reading is not a wrong number on a screen — it is the car changing what it will let the battery do. Temperature sets the charging rate, the power available, and whether fast charging is permitted at all. So a sensor reading falsely high makes a healthy pack behave like a tired one, and a sensor reading falsely low is the more dangerous direction, because the protection that should intervene does not.
As with the voltage sense circuits, these are thin wires on small connectors inside a sealed box, and they fail the same way.
Likely causes
Start here
- Faulty battery temperature sensor · specialist
- Corroded or loose connector · easy
Less common
- Damaged cell voltage sense harness · specialist
- Faulty battery pack sensor module · 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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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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