P0AC8 code meaning
Hybrid/EV Battery Temperature Sensor B Circuit High
Powertrain system Generic code P0Axx codes Check engine light
What P0AC8 means
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.
P0AC8 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0AC8
- Check engine or hybrid warning light
- Battery too cold message although it is not cold
- Strongly reduced charging and electric power
Common causes of P0AC8
- Most likelyOpen signal or return wire of sensor B
- PossibleThermistor open internally
- PossibleController software issue on the Volt (bulletin 18-NA-342)
- Less likelySignal shorted to the reference voltage
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv battery temp sensor bWiring harnessBms
What each part of P0AC8 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A | Area: hybrid propulsion. |
| C8 | The exact fault in that area. |
What to do next
- Note P0AC8 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0AC8
What does P0AC8 mean?
P0AC8 means "Hybrid/EV Battery Temperature Sensor B Circuit High". P0AC8 reports that battery temperature sensor B delivers a voltage above its valid range, which for an NTC thermistor reads as extreme cold. It is a generic code, so it means the same on every make.
Is it safe to drive with P0AC8?
Drive gently and only to a workshop. With P0AC8 the car can go into limp mode (reduced power) to protect itself.
Will P0AC8 fail an emissions test?
Yes, it can. P0AC8 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0AC8 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 5 hours of work. This is a job for a workshop.
Will P0AC8 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.