Powertrain, generic · Hybrid propulsion

P0C8B Hybrid/EV Battery Temperature Sensor I Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P0C8B covers a sensor I signal stuck above its valid voltage, which the controller interprets as extreme cold. An interrupted circuit lets the pull-up lift the line, so the root cause is usually an open connection or a failed thermistor rather than the weather. On the 2016 Cadillac ELR (16OBDG01) GM fails it below −40 °C, an ADC count above 3992, for 1.4 s within 2 s, two trips. Mitsubishi's 2018 Outlander PHEV declares channel [08] open beyond 3.97 V, colder than −62 °C, held 2 s. For the Volt, bulletin 18-NA-342 lists it as sensor 9 circuit high voltage among codes that can come with a Battery Too Cold message above −25 °C and recommends new module software. The short-circuit counterpart is P0C8A.

Likely causes

Open wire or loose connector in the sensor I circuit
Thermistor I open
Battery module software causing false cold readings (GM Volt, 18-NA-342)

Symptoms

  • Battery-too-cold message although outside temperature is mild
  • Electric drive limited or unavailable
  • Battery heater running unnecessarily

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,500
Time0.5–5 h

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

Parts involved

hv battery temp sensor iwiring harnessbms

Related codes

P0C8AP0C89P0C88P0C8CP0C84

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