P0A27Hybrid/EV Battery Power Off Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0A27 covers the circuit that tells the high-voltage battery to drop off the bus, i.e. the command path that opens the main contactors at key-off, after a fault or after a crash signal. Patents describe such a path as a dedicated hardware line in addition to CAN, so the contactors open within milliseconds. The code sets when commanded and actual state disagree. Honda lists P0A27 as High Voltage Contactor Stays Activated on the 2012-15 Civic Hybrid, where it is one of the codes that call for replacing the motor power inverter. P0A28 and P0A29 are the low and high voltage faults of the same line. The driver may see a hybrid warning and the car may refuse to start or power down.
- What you may notice
- Hybrid system warning or check engine light
- Vehicle will not enter ready mode or shuts down while driving
- High-voltage system does not power down after key-off
- Likely causes
- LikelyContactor or its driver does not release when power-off is commanded
- PossibleInternal fault in the inverter/power unit that controls the contactors (Honda Civic Hybrid)
- PossibleDamaged wiring or loose terminal on the hardwired power-off line
- RareCrash or emergency shutdown signal stored or still active
- 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: €150 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.