P0C91 code meaning
Hybrid/EV Battery Temperature Sensor J Circuit Intermittent/Erratic
Powertrain system Generic code P0Cxx codes Check engine light
What P0C91 means
P0C91 watches for a sensor J reading that changes too fast and too often for a heavy battery. GM's tables 16OBDG02 and 19OBDG02 add up how far the value moves between samples over a 10-sample window taken every 100 ms; a sum above 10 fails the window, and 4 failing windows out of 5, about half a second, store the code, Type B over two trips. The check needs more than 10.2 V and working communication. The reading may stay within its valid range, which distinguishes P0C91 from P0C8F and P0C90. Mitsubishi's PHEV has nothing comparable for this channel. Likely culprits are a worn contact or a conductor broken under its insulation; if neighbouring sensors jump at the same moment, suspect the monitoring board.
P0C91 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0C91
- Warning lamp that comes and goes between drives
- Sensor J value jumping in live data
Common causes of P0C91
- Most likelyFretting or loose terminal in the sensor J plug
- PossibleConductor broken inside the insulation, opening under vibration
- Less likelyUnstable reference or ground on the monitoring board
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 jWiring harnessBms
What each part of P0C91 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| C | Area: hybrid propulsion. |
| 91 | The exact fault in that area. |
What to do next
- Note P0C91 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 P0C91
What does P0C91 mean?
P0C91 means "Hybrid/EV Battery Temperature Sensor J Circuit Intermittent/Erratic". P0C91 watches for a sensor J reading that changes too fast and too often for a heavy battery. It is a generic code, so it means the same on every make.
Is it safe to drive with P0C91?
Drive gently and only to a workshop. With P0C91 the car can go into limp mode (reduced power) to protect itself.
Will P0C91 fail an emissions test?
Yes, it can. P0C91 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 P0C91 to fix?
Difficulty: workshop only. A typical repair takes 1 to 5 hours of work. This is a job for a workshop.
Will P0C91 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.