Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
The cost to diagnose the P0AA9 CADILLAC code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
Vehicles equipped with high voltage storage and propulsion capability are designed with high voltage circuits isolated from the vehicle chassis. If either the positive or negative high voltage Direct Current (DC) circuits or any of the high voltage Alternating Current (AC) phase circuits lose this isolation to the vehicle chassis, one or more Diagnostic Trouble Codes (DTC) may be set.
The Hybrid/EV Powertrain Control Module 2 performs active isolation testing to monitor the internal Hybrid/EV battery pack HV circuits for chassis isolation. The Hybrid/EV Powertrain Control Module 2 switches fixed resistors between the high voltage system and vehicle chassis. The difference between the switched-to-chassis state and the unswitched state is used to calculate a resistance-to-chassis value. The DTC will be set when the Isolation sensor voltage is less than 5 V.
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