P2C86Hybrid/EV Battery Voltage Internal Isolation Warning
- Generic OBD-II code · Powertrain
- How the car detects it
- P2C86 is an early warning that the insulation inside the traction battery, between cells, busbars or module electronics and the pack housing, is dropping but has not yet reached the fault limit. The full internal fault is P0E74. No manufacturer documents P2C86 publicly. Mercedes-Benz shows the same content under its own code P142900 (warning, insulation inside the battery) on its 2015-2020 plug-in hybrids. How internal and external are told apart is explained in a Tesla tech note: the battery management system measures inside the contactors, so a low reading with contactors open points to the pack itself, and below 1,800 kOhm in that state the pack was replaced. Coolant or condensation in the pack and damaged module wiring are typical. CARB counts isolation detection as safety-only.
- What you may notice
- Battery or high-voltage service message, often without immediate limits
- Charging may be refused if the value keeps falling
- Likely causes
- LikelyCoolant leaking inside the battery pack
- PossibleCondensation or water ingress through a failed pack seal or vent
- PossibleDamaged cell sensing or busbar insulation inside the pack
- RareIsolation measurement in the battery controller drifting
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €200 – €12,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.