OBD-II code · Powertrain (generic)
P0AA4 Hybrid Battery Negative Contactor Circuit
BMS detects an electrical fault in the negative HV contactor coil circuit.
Is it safe to drive with P0AA4?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyContactor coil open
Repair at a glance
- Difficulty
- Shop_only
- DIY friendly
- Best left to a mechanic
- Typical labour
- 2–8 h
- Emissions test
- Usually unaffected
- Parts involved
- Hv Contactor Negative, Bms
Related codes
- P0AA1Hybrid Battery Positive Contactor Circuit
- P0AA2Hybrid/EV Battery Positive Contactor Circuit Stuck Open
- P0AA3Hybrid/EV Battery Negative Contactor Circuit
- P0AA5Hybrid/EV Battery Negative Contactor Circuit Stuck Open
- P0AA6Hybrid Battery Voltage System Isolation Fault
- P0AA7Hybrid/EV Battery Voltage Isolation Sensor Circuit
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.