P0AC8Hybrid/EV Battery Temperature Sensor B 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
- P0AC8 reports that battery temperature sensor B delivers a voltage above its valid range, which for an NTC thermistor reads as extreme cold. An open wire, a disconnected sensing board plug or a broken sensor are typical. GM's 2016 and 2019 tables set it below -69 °C in 8 of 10 samples, the two-mode hybrid tables of 2011 and 2013 below -45 °C in 30 of 40, and GM's 2013 table 13OBDG05C above 4.63 V, about -45 °C, in 7 of 10; all Type B, two trips. In the Chevrolet Volt, bulletin 18-NA-342 links such codes to a Battery Too Cold message above -25 °C ambient and prescribes reprogramming. A pack believed to be frozen gets strict charge and power limits.
- What you may notice
- Check engine or hybrid warning light
- Battery too cold message although it is not cold
- Strongly reduced charging and electric power
- Likely causes
- LikelyOpen signal or return wire of sensor B
- PossibleThermistor open internally
- PossibleController software issue on the Volt (bulletin 18-NA-342)
- RareSignal shorted to the reference voltage
- 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.