Conditions for Setting the DTC
WARNING: This page is about a different car, the 2019 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
The difference between the Isolation Supply voltage sensed and hybrid battery voltage is greater than 70 V.
And
The difference between the Isolation Supply voltage sensed and the high voltage measured is greater than 70 V.