Monitor Description
WARNING: This page is about a different car, the 2004 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
The HV control ECU performs many diagnostic tests to verify proper operation of internal ECU systems. In one of these diagnostics, the HV control ECU performs a self-test.
If the HV control ECU detects an internal problem during this self-test, it will conclude that there is an internal malfunction. The HV control ECU will illuminate the MIL and set a DTC.