P0A9BHybrid/EV Battery Temperature Sensor A Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- Temperature sensor A is one of the thermistors the battery controller uses to track cell or module temperature for cooling, charge limits and power limits. P0A9B is the general circuit code for this sensor: the controller finds an electrical fault it does not classify further as low, high or erratic. No manufacturer documents this exact code publicly; GM, for example, reports the sibling codes P0A9C to P0A9F instead. In those tables a failed sensor input is excluded from protection logic, and GM's Volt bulletin notes several sensors per pack. Expect a hybrid warning and reduced charge and assist power while the controller works with fewer valid temperatures. Check the sensor harness at the module sensing board before condemning the pack.
- What you may notice
- Hybrid or EV system warning and check engine light
- Reduced electric assist, regeneration or charging power
- Battery cooling fan or pump runs more than usual
- Likely causes
- LikelyOpen, corroded or loose sensor wiring or connector inside the pack
- PossibleFailed thermistor on the module or cell sensing board
- RareBattery controller input or software fault
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €150 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.