Our automotive experts have put together the following information about the P0AA9 diagnostic trouble code. We've provided the common symptoms that occur when this code is set along with the frequent repairs that address the issues related to the P0AA9 code.

OBD II Fault Code

  • OBD II P0AA9

    OBD-II Code High voltage system may not operate is defined as a Hybrid Battery Voltage Isolation Sensor Circuit Low

    The high voltage system uses a battery voltage isolation sensor inside the battery control module to monitor separation of the high and low voltage systems. If sensor fails, P0AA9 will set. The high voltage system may become disabled.

    High voltage system may not operate Symptoms

    • High voltage system may not operate
    • Vehicle will not charge

    Common Problems That Trigger the P0AA9 Code

    • Battery Smart Unit failure
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