Powertrain, generic · Hybrid propulsion

P0AC8 Hybrid/EV Battery Temperature Sensor B Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

Open signal or return wire of sensor B
Thermistor open internally
Controller software issue on the Volt (bulletin 18-NA-342)
Signal shorted to the reference voltage

Symptoms

  • Check engine or hybrid warning light
  • Battery too cold message although it is not cold
  • Strongly reduced charging and electric power

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€60–2,500
Time0.5–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hv battery temp sensor bwiring harnessbms

Related codes

P0AC7P0AC5P0AC6P0AC9P0A9EP0ACD

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.