Powertrain, generic · Hybrid propulsion

P0C81 Hybrid/EV Battery Temperature Sensor H Circuit

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

P0C81 reports an electrical fault on the input of battery temperature sensor H that the controller does not narrow down further. No manufacturer documents this exact code publicly. In GM's Volt pack sensor H is sensor 8 (bulletin 18-NA-342), and both the 2016 Cadillac ELR table (16OBDG01) and the later Volt tables list only the specific H codes P0C82 to P0C85. Regulators still expect the input to be watched: CARB section (e)(15.3.1) requires continuous monitoring of value range and circuit continuity for such sensors. If the controller cannot trust H it treats the affected cell group as at risk and limits battery power until the fault clears. A generic circuit code calls for a full check of the wiring and connector from the thermistor to the sensing board, inside the HV pack.

Likely causes

Poor contact at the sensor H connector

Thermistor H defective

Damaged measuring channel on the sensing board

Symptoms

Hybrid or EV warning lamp
Limited acceleration in electric mode
Charging slower than usual

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€150–2,500

Time1–5 h

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

Parts involved

hv battery temp sensor hwiring harnessbms

References: law.cornell.edu, static.nhtsa.gov, gsi.ext.gm.com.