OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P0AA6

Hybrid Battery Voltage System Isolation Fault

The BMS isolation monitor detects insulation resistance between HV positive/negative bus and chassis ground below the safe threshold, indicating insulation failure somewhere in the HV system.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / numberA / A6

Possible causes

  • HV cable insulation damaged high
  • Moisture intrusion in HV component medium
  • Aged HV component insulation low

Inspection / repair

  • Difficulty: shop only
  • DIY: shop recommended
  • Estimated cost: 600–6000 €
  • Estimated time: 3–14 h
  • Component: hv battery
  • Component: hv cabling
  • Component: inverter
  • Component: charger
  • MIL / check engine light
  • limp mode possible

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication