P2C88Hybrid/EV Battery Voltage System Isolation Warning
- Generic OBD-II code · Powertrain
- Can trigger limp mode
- How the car detects it
- P2C88 is the warning counterpart to P0AA6: the isolation resistance of the high-voltage system as a whole has fallen below a first limit without the monitor yet being able to say whether the battery or the vehicle side is to blame. Mercedes-Benz uses P2C8800 in the battery management system of the 295, 296 and 297 model series; its 2025 bulletin lists it with P2C8500 and P2C8700 when moisture builds up in a high-voltage PTC heater lacking a diaphragm, a fault that starts sporadically and worsens. Legally the complete system must stay above 500 ohms per volt, so the warning leaves time to find the leak before a lockout. Measure each branch separately, starting with components that are switched in only at times.
- What you may notice
- High-voltage warning message, sometimes towing not allowed notice
- Electric heater stays cold if it is the leaking part
- Likely causes
- LikelyMoisture in a high-voltage component that is only switched in at times (heater, compressor)
- PossibleGradual insulation aging in cables or connectors
- RareBeginning insulation loss inside the battery pack
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €200 – €4,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.