P0C85 points to a sensor H reading that flickers. A battery pack warms and cools slowly, so fast swings in one channel suggest an electrical contact problem rather than real heat. GM's 2018 hybrid table 18OBDG02 adds up how much the value moves within a 10-sample window at 100 ms per sample; once that sum passes 10 in 4 of 5 evaluations, the module logs P0C85, Type B over two trips, as long as the supply exceeds 10.2 V and the battery interface module is talking. The 2019 table 19OBDG02 keeps the same rule. GM's OBDG01 tables of 2011 to 2016 (first-generation Volt, ELR) and Mitsubishi list no such code for sensor H. A wiggle test on the harness while watching live data usually finds the fault; low or high voltage faults are P0C83 and P0C84 instead.
High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.
Symptoms
- Intermittent warning lamp
- Sensor H value jumping in live data
Most likely causes
- Intermittent contact at the sensor H terminal
- Partly broken sensor H wire inside the pack harness
- Noisy measuring channel on the sensing board
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- It can trigger limp mode.
- It affects emissions.
What each character of P0C85 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- C: Subsystem depends on the code range
- 85: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0C85?
If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.
What causes code P0C85?
The most common causes are: intermittent contact at the sensor H terminal; partly broken sensor H wire inside the pack harness; noisy measuring channel on the sensing board.
Related codes
- P0C81Hybrid/EV Battery Temperature Sensor H Circuit
- P0C82Hybrid/EV Battery Temperature Sensor H Circuit Range/Performance
- P0C83Hybrid/EV Battery Temperature Sensor H Circuit Low
- P0C84Hybrid/EV Battery Temperature Sensor H Circuit High
- P0C80Hybrid/EV Battery Temperature Sensor G Circuit Intermittent/Erratic
- P0C8CHybrid/EV Battery Temperature Sensor I Circuit Intermittent/Erratic
Sources
- gsi.ext.gm.com: 18OBDG02 Hybrid Diagnostics
- gsi.ext.gm.com: 19OBDG02 Hybrid Diagnostics
- law.cornell.edu: 13 CCR 1968.2
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.