P0C91Hybrid/EV Battery Temperature Sensor J Circuit Intermittent/Erratic
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Warning lamp that comes and goes between drives
- Sensor J value jumping in live data
- Likely causes
- LikelyFretting or loose terminal in the sensor J plug
- PossibleConductor broken inside the insulation, opening under vibration
- RareUnstable reference or ground on the monitoring board
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.