P0A9EHybrid/EV Battery Temperature Sensor A Circuit High
- 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
- With the NTC thermistor of sensor A on a pull-up circuit, an open sensor or wire drives the input voltage toward the reference, which the controller reads as an extremely cold cell. GM sets P0A9E (Type B, two trips) when the value falls below -69 °C in 8 of 10 samples (19OBDG02); Two-Mode hybrids flag readings below -45 °C, other programs below -40 °C for 1.4 s. GM's Volt bulletin 18-NA-342 lists it as sensor 1 circuit high voltage and pairs it with a battery too cold message at mild ambient temperatures. Unlike P0A9D the fault suggests an open circuit rather than a short. Because cold cells accept little current, the car restricts charging, regeneration and electric drive.
- What you may notice
- Check engine or hybrid warning light
- Battery too cold message although it is not cold
- Little or no electric drive and weak regeneration
- Likely causes
- LikelyOpen sensor wire or unplugged connector inside the pack
- PossibleOpen (failed) thermistor on the sensing board
- RareSignal shorted to the reference voltage
- RareBattery controller software causing false sets (GM Volt)
- 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: €60 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.